diff --git a/src/des.c b/src/des.c
index 408b331e..0aab160c 100644
--- a/src/des.c
+++ b/src/des.c
@@ -175,7 +175,7 @@ void des_set_encrypt_key(DES_KEY *key, const unsigned char user_key[8])
 
 	K = GETU64(user_key);
 	K = permute(PC1, sizeof(PC1), K);
-	L = K >> 28;
+	L = (K >> 28) & 0xffffffff;
 	R = K & 0x0fffffff;
 
 	for (i = 0; i < 16; i++) {
@@ -217,7 +217,7 @@ void des_encrypt(DES_KEY *key, const unsigned char in[DES_BLOCK_SIZE],
 		T ^= L;
 
 		L = R;
-		R = T;
+		R = T & 0xffffffff;
 	}
 
 	T = ((uint64_t)L << 32) | R;
diff --git a/src/pkcs8.c b/src/pkcs8.c
index 636ec774..8ff193ba 100644
--- a/src/pkcs8.c
+++ b/src/pkcs8.c
@@ -353,7 +353,6 @@ int pbes2_algor_from_der(
 	int ret;
 	const uint8_t *d;
 	size_t dlen;
-	int oid;
 	uint32_t nodes[32];
 	size_t nodes_cnt;
 
diff --git a/src/skf/skf.c b/src/skf/skf.c
index d9c0f1ae..08fed460 100755
--- a/src/skf/skf.c
+++ b/src/skf/skf.c
@@ -536,8 +536,8 @@ int skf_import_object(SKF_DEVICE *dev, const char *appname, const char *pin,
 		error_print();
 		return -1;
 	}
-	if (SKF_CreateFile(hApp, (LPSTR)objname, datalen, ulReadRights, ulWriteRights) != SAR_OK
-		|| SKF_WriteFile(hApp, (LPSTR)objname, 0, (BYTE *)data, datalen) != SAR_OK) {
+	if (SKF_CreateFile(hApp, (LPSTR)objname, (ULONG)datalen, ulReadRights, ulWriteRights) != SAR_OK
+		|| SKF_WriteFile(hApp, (LPSTR)objname, 0, (BYTE *)data, (ULONG)datalen) != SAR_OK) {
 		error_print();
 		goto end;
 	}
@@ -554,7 +554,6 @@ int skf_export_object(SKF_DEVICE *dev, const char *appname, const char *pin,
 	HAPPLICATION hApp = NULL;
 	FILEATTRIBUTE fileInfo;
 	ULONG ulen;
-	int len;
 
 	if (!dev || !appname || !pin || !objname || !outlen) {
 		error_print();
diff --git a/src/skf/skf_dummy.c b/src/skf/skf_dummy.c
index 3d1e88b6..d84b10f3 100755
--- a/src/skf/skf_dummy.c
+++ b/src/skf/skf_dummy.c
@@ -1,12 +1,12 @@
-/*
- *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
- *
- *  Licensed under the Apache License, Version 2.0 (the License); you may
- *  not use this file except in compliance with the License.
- *
- *  http://www.apache.org/licenses/LICENSE-2.0
- */
-
+/*
+ *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the License); you may
+ *  not use this file except in compliance with the License.
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ */
+
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -434,7 +434,7 @@ ULONG DEVAPI SKF_ExportCertificate(
 	BYTE *pbCert,
 	ULONG *pulCertLen)
 {
-	*pulCertLen = strlen(sm2cert_pemstr);
+	*pulCertLen = (ULONG)strlen(sm2cert_pemstr);
 	memcpy(pbCert, sm2cert_pemstr, *pulCertLen);
 
 	return SAR_OK;
diff --git a/src/sm2_lib.c b/src/sm2_lib.c
index 27ffd46e..8557d466 100644
--- a/src/sm2_lib.c
+++ b/src/sm2_lib.c
@@ -492,13 +492,12 @@ int sm2_do_encrypt(const SM2_KEY *key, const uint8_t *in, size_t inlen, SM2_CIPH
 
 int sm2_do_decrypt(const SM2_KEY *key, const SM2_CIPHERTEXT *in, uint8_t *out, size_t *outlen)
 {
-	uint32_t inlen;
+	uint32_t inlen, i;
 	SM2_BN d;
 	SM2_JACOBIAN_POINT _P, *P = &_P;
 	SM3_CTX sm3_ctx;
 	uint8_t buf[64];
 	uint8_t hash[32];
-	int i;
 
 	// FIXME: check SM2_CIPHERTEXT format
 
diff --git a/src/sm9_alg.c b/src/sm9_alg.c
index 6a21dfc0..735a4ccb 100644
--- a/src/sm9_alg.c
+++ b/src/sm9_alg.c
@@ -126,7 +126,7 @@ void sm9_bn_to_bits(const sm9_bn_t a, char bits[256])
 {
 	int i, j;
 	for (i = 7; i >= 0; i--) {
-		uint32_t w = a[i];
+		uint32_t w = (uint32_t)a[i];
 		for (j = 0; j < 32; j++) {
 			*bits++ = (w & 0x80000000) ? '1' : '0';
 			w <<= 1;
diff --git a/src/tls.c b/src/tls.c
index 3a31fa79..206f0976 100644
--- a/src/tls.c
+++ b/src/tls.c
@@ -1483,7 +1483,11 @@ int tls_record_send(const uint8_t *record, size_t recordlen, int sock)
 		error_print();
 		return -1;
 	}
+#ifdef WIN32
+	if ((r = send(sock, record, (int)recordlen, 0)) < 0) {
+#else	
 	if ((r = send(sock, record, recordlen, 0)) < 0) {
+#endif
 		perror("tls_record_send");
 		error_print();
 		return -1;
@@ -1509,7 +1513,11 @@ int tls_record_do_recv(uint8_t *record, size_t *recordlen, int sock)
 
 	len = 5;
 	while (len) {
+#ifdef WIN32
+		if ((r = recv(sock, record + 5 - len, (int)len, 0)) < 0) {
+#else
 		if ((r = recv(sock, record + 5 - len, len, 0)) < 0) {
+#endif
 			perror("tls_record_do_recv");
 			error_print();
 			return -1;
@@ -1538,7 +1546,11 @@ int tls_record_do_recv(uint8_t *record, size_t *recordlen, int sock)
 		return -1;
 	}
 	while (len) {
+#ifdef WIN32
+		if ((r = recv(sock, record + *recordlen - len, (int)len, 0)) < 0) {
+#else
 		if ((r = recv(sock, record + *recordlen - len, len, 0)) < 0) {
+#endif
 			perror("tls_record_do_recv");
 			error_print();
 			return -1;
diff --git a/src/tls_ext.c b/src/tls_ext.c
index db84a17d..9f1ae0ac 100644
--- a/src/tls_ext.c
+++ b/src/tls_ext.c
@@ -502,7 +502,6 @@ int tls13_process_client_supported_versions(const uint8_t *ext_data, size_t ext_
 	const uint8_t *versions;
 	size_t versions_len;
 	int selected_version = -1;
-	size_t len;
 
 	if (tls_uint8array_from_bytes(&versions, &versions_len, &ext_data, &ext_datalen) != 1
 		|| tls_length_is_zero(ext_datalen) != 1) {
@@ -644,7 +643,7 @@ int tls13_server_key_share_ext_to_bytes(const SM2_POINT *point, uint8_t **out, s
 	}
 	tls13_key_share_entry_to_bytes(point, NULL, &ext_datalen);
 	tls_uint16_to_bytes(ext_type, out, outlen);
-	tls_uint16_to_bytes(ext_datalen, out, outlen);
+	tls_uint16_to_bytes((uint16_t)ext_datalen, out, outlen);
 	tls13_key_share_entry_to_bytes(point, out, outlen);
 	return 1;
 }
@@ -694,8 +693,8 @@ int tls13_client_key_share_ext_to_bytes(const SM2_POINT *point, uint8_t **out, s
 	ext_datalen = tls_uint16_size() + client_shares_len;
 
 	tls_uint16_to_bytes(ext_type, out, outlen);
-	tls_uint16_to_bytes(ext_datalen, out, outlen);
-	tls_uint16_to_bytes(client_shares_len, out, outlen);
+	tls_uint16_to_bytes((uint16_t)ext_datalen, out, outlen); // FIXME: do we need to check length < UINT16_MAX?
+	tls_uint16_to_bytes((uint16_t)client_shares_len, out, outlen);
 	tls13_key_share_entry_to_bytes(point, out, outlen);
 	return 1;
 }
@@ -791,8 +790,8 @@ int tls13_certificate_authorities_ext_to_bytes(const uint8_t *ca_names, size_t c
 	ext_datalen = tls_uint16_size() + authorities_len;
 
 	tls_uint16_to_bytes(ext_type, out, outlen);
-	tls_uint16_to_bytes(ext_datalen, out, outlen);
-	tls_uint16_to_bytes(authorities_len, out, outlen);
+	tls_uint16_to_bytes((uint16_t)ext_datalen, out, outlen);
+	tls_uint16_to_bytes((uint16_t)authorities_len, out, outlen);
 	while (ca_names_len) {
 		x509_name_from_der(&name, &namelen, &ca_names, &ca_names_len);
 		tls_uint16array_to_bytes(name, namelen, out, outlen);
diff --git a/src/tls_trace.c b/src/tls_trace.c
index 31c210f0..c9a95430 100644
--- a/src/tls_trace.c
+++ b/src/tls_trace.c
@@ -325,7 +325,6 @@ const char *tls_signature_scheme_name(int scheme)
 
 int tls_random_print(FILE *fp, const uint8_t random[32], int format, int indent)
 {
-	int i;
 	time_t gmt_unix_time = 0;
 	const uint8_t *cp = random;
 	size_t len = 4;
@@ -590,7 +589,6 @@ int tls_server_hello_print(FILE *fp, const uint8_t *data, size_t datalen, int fo
 	uint8_t comp_meth;
 	const uint8_t *exts;
 	size_t session_id_len, cipher_suites_len, comp_meths_len, exts_len;
-	size_t i;
 
 	format_print(fp, format, indent, "ServerHello\n"); indent += 4;
 	if (tls_uint16_from_bytes(&protocol, &data, &datalen) != 1) goto bad;
@@ -620,7 +618,6 @@ bad:
 
 int tls_certificate_print(FILE *fp, const uint8_t *data, size_t datalen, int format, int indent)
 {
-	int ret;
 	const uint8_t *certs;
 	size_t certslen;
 	const uint8_t *der;
@@ -752,7 +749,7 @@ int tls_certificate_request_print(FILE *fp, const uint8_t *data, size_t datalen,
 {
 	const uint8_t *cert_types;
 	const uint8_t *ca_names;
-	size_t cert_types_len, ca_names_len, i;
+	size_t cert_types_len, ca_names_len;
 
 	format_print(fp, format, indent, "CertificateRequest\n"); indent += 4;
 	if (tls_uint8array_from_bytes(&cert_types, &cert_types_len, &data, &datalen) != 1) goto bad;
diff --git a/tests/chacha20test.c b/tests/chacha20test.c
index b6a105d4..e88eebb0 100644
--- a/tests/chacha20test.c
+++ b/tests/chacha20test.c
@@ -18,7 +18,6 @@
 int main(void)
 {
 	int err = 0;
-	int i;
 	const unsigned char key[] = {
 		0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
 		0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
diff --git a/tests/pkcs8test.c b/tests/pkcs8test.c
index f1c59d54..dd02647f 100644
--- a/tests/pkcs8test.c
+++ b/tests/pkcs8test.c
@@ -375,8 +375,6 @@ static int test_pkcs8_pem(void)
 	char *pass = "password";
 	SM2_KEY sm2_key;
 	SM2_KEY sm2_buf;
-	const uint8_t *attrs;
-	size_t attrs_len;
 	FILE *fp;
 
 	sm2_key_generate(&sm2_key);
diff --git a/tests/sm3test.c b/tests/sm3test.c
index f67d2ba3..66dad8cd 100644
--- a/tests/sm3test.c
+++ b/tests/sm3test.c
@@ -141,7 +141,6 @@ static int test_sm3(void)
 	};
 
 	int err = 0;
-	char *p;
 	uint8_t testbuf[sizeof(testhex)/2 + 1000];
 	uint8_t dgstbuf[32];
 	size_t testbuflen, dgstbuflen;
@@ -156,7 +155,7 @@ static int test_sm3(void)
 
 		if (memcmp(dgstbuf, dgst, sizeof(dgst)) != 0) {
 			int n;
-			fprintf(stderr, "sm3 test %lu failed\n", i+1);
+			fprintf(stderr, "sm3 test %zu failed\n", i+1);
 			fprintf(stderr, "error calculating SM3 on %s\n", testhex[i]);
 			fprintf(stderr, " digest(corret) = ");
 			for (n = 0; n < sizeof(dgst); n++) {
diff --git a/tests/sm4test.c b/tests/sm4test.c
index 58bf8a11..4f5c08b0 100644
--- a/tests/sm4test.c
+++ b/tests/sm4test.c
@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
  *
  *  Licensed under the Apache License, Version 2.0 (the License); you may
diff --git a/tests/zuctest.c b/tests/zuctest.c
index f58c2cea..1bcd5b22 100644
--- a/tests/zuctest.c
+++ b/tests/zuctest.c
@@ -421,7 +421,7 @@ int zuc256_mac_test(void)
 		{0xa35bb274,0xb567c48b,0x28319f11,0x1af34fbd},
 		{0x3a83b554,0xbe408ca5,0x494124ed,0x9d473205},
 	};
-	int i, j;
+	unsigned int i, j;
 
 	bswap_buf((uint32_t *)tag32, sizeof(tag32)/4);
 	bswap_buf((uint32_t *)tag64, sizeof(tag64)/4);
diff --git a/tools/tlcp_client.c b/tools/tlcp_client.c
index e4961c2d..a53cd22b 100644
--- a/tools/tlcp_client.c
+++ b/tools/tlcp_client.c
@@ -59,7 +59,6 @@ int tlcp_client_main(int argc, char *argv[])
 	char buf[1024] = {0};
 	size_t len = sizeof(buf);
 	char send_buf[1024] = {0};
-	size_t send_len;
 
 	argc--;
 	argv++;
@@ -161,7 +160,8 @@ bad:
 		FD_SET(conn.sock, &fds);
 		FD_SET(fileno(stdin), &fds); //FD_SET(STDIN_FILENO, &fds);
 
-		if (select(conn.sock + 1, &fds, NULL, NULL, NULL) < 0) {
+		if (select((int)(conn.sock + 1), // WinSock2 select() ignore this arg
+			&fds, NULL, NULL, NULL) < 0) {
 			fprintf(stderr, "%s: select failed\n", prog);
 			goto end;
 		}
diff --git a/tools/tls12_client.c b/tools/tls12_client.c
index 2f2df760..4ac0e16e 100644
--- a/tools/tls12_client.c
+++ b/tools/tls12_client.c
@@ -161,7 +161,7 @@ bad:
 		FD_SET(conn.sock, &fds);
 		FD_SET(fileno(stdin), &fds);
 
-		if (select(conn.sock + 1, &fds, NULL, NULL, NULL) < 0) {
+		if (select((int)(conn.sock + 1), &fds, NULL, NULL, NULL) < 0) {
 			fprintf(stderr, "%s: select failed\n", prog);
 			goto end;
 		}
diff --git a/tools/tls12_server.c b/tools/tls12_server.c
index 48f96840..d983021a 100644
--- a/tools/tls12_server.c
+++ b/tools/tls12_server.c
@@ -40,7 +40,6 @@ int tls12_server_main(int argc , char **argv)
 	char *cacertfile = NULL;
 
 	int server_ciphers[] = { TLS_cipher_ecdhe_sm4_cbc_sm3, };
-	uint8_t verify_buf[4096];
 
 	TLS_CTX ctx;
 	TLS_CONNECT conn;
diff --git a/tools/tls13_client.c b/tools/tls13_client.c
index 66cdf330..b6e9767e 100644
--- a/tools/tls13_client.c
+++ b/tools/tls13_client.c
@@ -59,7 +59,6 @@ int tls13_client_main(int argc, char *argv[])
 	char buf[1024] = {0};
 	size_t len = sizeof(buf);
 	char send_buf[1024] = {0};
-	size_t send_len;
 
 	argc--;
 	argv++;
@@ -158,7 +157,8 @@ bad:
 		FD_SET(conn.sock, &fds);
 		FD_SET(fileno(stdin), &fds);
 
-		if (select(conn.sock + 1, &fds, NULL, NULL, NULL) < 0) {
+		if (select((int)(conn.sock + 1), // In WinSock2, select() ignore the this arg
+			&fds, NULL, NULL, NULL) < 0) {
 			fprintf(stderr, "%s: select failed\n", prog);
 			goto end;
 		}
diff --git a/tools/tls13_server.c b/tools/tls13_server.c
index 60219269..ca0ff93d 100644
--- a/tools/tls13_server.c
+++ b/tools/tls13_server.c
@@ -40,8 +40,7 @@ int tls13_server_main(int argc , char **argv)
 	char *cacertfile = NULL;
 
 	int server_ciphers[] = { TLS_cipher_sm4_gcm_sm3, };
-	uint8_t verify_buf[4096];
-
+	
 	TLS_CTX ctx;
 	TLS_CONNECT conn;
 	char buf[1600] = {0};