diff --git a/sm4/sm4.go b/sm4/sm4.go
index 0e301deb..04c78388 100644
--- a/sm4/sm4.go
+++ b/sm4/sm4.go
@@ -27,7 +27,7 @@ import (
 
 const BlockSize = 16
 
-var IV = make([]byte, BlockSize)
+var errIVLen = errors.New("SM4: invalid iv size")
 
 type SM4Key []byte
 
@@ -291,26 +291,21 @@ func pkcs7UnPadding(src []byte) ([]byte, error) {
 
 	return src[:(length - unpadding)], nil
 }
-func SetIV(iv []byte) error {
-	if len(iv) != BlockSize {
-		return errors.New("SM4: invalid iv size")
-	}
-	IV = iv
-	return nil
-}
 
-func Sm4Cbc(key []byte, in []byte, mode bool) (out []byte, err error) {
+func Sm4Cbc(key []byte, iv []byte, in []byte, mode bool) (out []byte, err error) {
 	if len(key) != BlockSize {
 		return nil, errors.New("SM4: invalid key size " + strconv.Itoa(len(key)))
 	}
+	if len(iv) != BlockSize {
+		return nil, errIVLen
+	}
+
 	var inData []byte
 	if mode {
 		inData = pkcs7Padding(in)
 	} else {
 		inData = in
 	}
-	iv := make([]byte, BlockSize)
-	copy(iv, IV)
 	out = make([]byte, len(inData))
 	c, err := NewCipher(key)
 	if err != nil {
@@ -376,10 +371,14 @@ func Sm4Ecb(key []byte, in []byte, mode bool) (out []byte, err error) {
 //密码反馈模式（Cipher FeedBack (CFB)）
 //https://blog.csdn.net/zy_strive_2012/article/details/102520356
 //https://blog.csdn.net/sinat_23338865/article/details/72869841
-func Sm4CFB(key []byte, in []byte, mode bool) (out []byte, err error) {
+func Sm4CFB(key []byte, iv []byte, in []byte, mode bool) (out []byte, err error) {
 	if len(key) != BlockSize {
 		return nil, errors.New("SM4: invalid key size " + strconv.Itoa(len(key)))
 	}
+	if len(iv) != BlockSize {
+		return nil, errIVLen
+	}
+
 	var inData []byte
 	if mode {
 		inData = pkcs7Padding(in)
@@ -399,7 +398,7 @@ func Sm4CFB(key []byte, in []byte, mode bool) (out []byte, err error) {
 	if mode { //加密
 		for i := 0; i < len(inData)/16; i++ {
 			if i == 0 {
-				c.Encrypt(K, IV)
+				c.Encrypt(K, iv)
 				cipherBlock = xor(K[:BlockSize], inData[i*16:i*16+16])
 				copy(out[i*16:i*16+16], cipherBlock)
 				//copy(cipherBlock,out_tmp)
@@ -415,7 +414,7 @@ func Sm4CFB(key []byte, in []byte, mode bool) (out []byte, err error) {
 		var i int = 0
 		for ; i < len(inData)/16; i++ {
 			if i == 0 {
-				c.Encrypt(K, IV)                                      //这里是加密，而不是调用解密方法Decrypt
+				c.Encrypt(K, iv)                                      //这里是加密，而不是调用解密方法Decrypt
 				plainBlock = xor(K[:BlockSize], inData[i*16:i*16+16]) //获取明文分组
 				copy(out[i*16:i*16+16], plainBlock)
 				continue
@@ -435,10 +434,14 @@ func Sm4CFB(key []byte, in []byte, mode bool) (out []byte, err error) {
 //输出反馈模式（Output feedback, OFB）
 //https://blog.csdn.net/chengqiuming/article/details/82390910
 //https://blog.csdn.net/sinat_23338865/article/details/72869841
-func Sm4OFB(key []byte, in []byte, mode bool) (out []byte, err error) {
+func Sm4OFB(key []byte, iv []byte, in []byte, mode bool) (out []byte, err error) {
 	if len(key) != BlockSize {
 		return nil, errors.New("SM4: invalid key size " + strconv.Itoa(len(key)))
 	}
+	if len(iv) != BlockSize {
+		return nil, errors.New("SM4: invalid iv size")
+	}
+
 	var inData []byte
 	if mode {
 		inData = pkcs7Padding(in)
@@ -459,7 +462,7 @@ func Sm4OFB(key []byte, in []byte, mode bool) (out []byte, err error) {
 	if mode { //加密
 		for i := 0; i < len(inData)/16; i++ {
 			if i == 0 {
-				c.Encrypt(K, IV)
+				c.Encrypt(K, iv)
 				cipherBlock = xor(K[:BlockSize], inData[i*16:i*16+16])
 				copy(out[i*16:i*16+16], cipherBlock)
 				copy(shiftIV, K[:BlockSize])
@@ -474,14 +477,14 @@ func Sm4OFB(key []byte, in []byte, mode bool) (out []byte, err error) {
 	} else { //解密
 		for i := 0; i < len(inData)/16; i++ {
 			if i == 0 {
-				c.Encrypt(K, IV)                                      //这里是加密，而不是调用解密方法Decrypt
-				plainBlock = xor(K[:BlockSize], inData[i*16:i*16+16]) //获取明文分组
+				c.Encrypt(K, iv)                                      // 这里是加密，而不是调用解密方法Decrypt
+				plainBlock = xor(K[:BlockSize], inData[i*16:i*16+16]) // 获取明文分组
 				copy(out[i*16:i*16+16], plainBlock)
 				copy(shiftIV, K[:BlockSize])
 				continue
 			}
 			c.Encrypt(K, shiftIV)
-			plainBlock = xor(K[:BlockSize], inData[i*16:i*16+16]) //获取明文分组
+			plainBlock = xor(K[:BlockSize], inData[i*16:i*16+16]) // 获取明文分组
 			copy(out[i*16:i*16+16], plainBlock)
 			copy(shiftIV, K[:BlockSize])
 		}
diff --git a/sm4/sm4_test.go b/sm4/sm4_test.go
index 6115ba14..cb9bd0c3 100644
--- a/sm4/sm4_test.go
+++ b/sm4/sm4_test.go
@@ -43,8 +43,6 @@ func TestSM4(t *testing.T) {
 	}
 	fmt.Printf("ecbMsg = %x\n", ecbMsg)
 	iv := []byte("0000000000000000")
-	err = SetIV(iv)
-	fmt.Printf("err = %v\n", err)
 	ecbDec, err := Sm4Ecb(key, ecbMsg, false)
 	if err != nil {
 		t.Errorf("sm4 dec error:%s", err)
@@ -54,12 +52,12 @@ func TestSM4(t *testing.T) {
 	if !testCompare(data, ecbDec) {
 		t.Errorf("sm4 self enc and dec failed")
 	}
-	cbcMsg, err := Sm4Cbc(key, data, true)
+	cbcMsg, err := Sm4Cbc(key, iv, data, true)
 	if err != nil {
 		t.Errorf("sm4 enc error:%s", err)
 	}
 	fmt.Printf("cbcMsg = %x\n", cbcMsg)
-	cbcDec, err := Sm4Cbc(key, cbcMsg, false)
+	cbcDec, err := Sm4Cbc(key, iv, cbcMsg, false)
 	if err != nil {
 		t.Errorf("sm4 dec error:%s", err)
 		return
@@ -69,26 +67,26 @@ func TestSM4(t *testing.T) {
 		t.Errorf("sm4 self enc and dec failed")
 	}
 
-	cbcMsg, err = Sm4CFB(key, data, true)
+	cbcMsg, err = Sm4CFB(key, iv, data, true)
 	if err != nil {
 		t.Errorf("sm4 enc error:%s", err)
 	}
 	fmt.Printf("cbcCFB = %x\n", cbcMsg)
 
-	cbcCfb, err := Sm4CFB(key, cbcMsg, false)
+	cbcCfb, err := Sm4CFB(key, iv, cbcMsg, false)
 	if err != nil {
 		t.Errorf("sm4 dec error:%s", err)
 		return
 	}
 	fmt.Printf("cbcCFB = %x\n", cbcCfb)
 
-	cbcMsg, err = Sm4OFB(key, data, true)
+	cbcMsg, err = Sm4OFB(key, iv, data, true)
 	if err != nil {
 		t.Errorf("sm4 enc error:%s", err)
 	}
 	fmt.Printf("cbcOFB = %x\n", cbcMsg)
 
-	cbcOfc, err := Sm4OFB(key, cbcMsg, false)
+	cbcOfc, err := Sm4OFB(key, iv, cbcMsg, false)
 	if err != nil {
 		t.Errorf("sm4 dec error:%s", err)
 		return