diff --git a/miniprogram/decrypt.go b/miniprogram/decrypt.go
new file mode 100644
index 0000000..6897368
--- /dev/null
+++ b/miniprogram/decrypt.go
@@ -0,0 +1,93 @@
+package miniprogram
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+)
+
+var (
+	// ErrAppIDNotMatch appid不匹配
+	ErrAppIDNotMatch = errors.New("app id not match")
+	// ErrInvalidBlockSize block size不合法
+	ErrInvalidBlockSize = errors.New("invalid block size")
+	// ErrInvalidPKCS7Data PKCS7数据不合法
+	ErrInvalidPKCS7Data = errors.New("invalid PKCS7 data")
+	// ErrInvalidPKCS7Padding 输入padding失败
+	ErrInvalidPKCS7Padding = errors.New("invalid padding on input")
+)
+
+// UserInfo 用户信息
+type UserInfo struct {
+	OpenID    string `json:"openId"`
+	UnionID   string `json:"unionId"`
+	NickName  string `json:"nickName"`
+	Gender    int    `json:"gender"`
+	City      string `json:"city"`
+	Province  string `json:"province"`
+	Country   string `json:"country"`
+	AvatarURL string `json:"avatarUrl"`
+	Language  string `json:"language"`
+	Watermark struct {
+		Timestamp int64  `json:"timestamp"`
+		AppID     string `json:"appid"`
+	} `json:"watermark"`
+}
+
+// pkcs7Unpad returns slice of the original data without padding
+func pkcs7Unpad(data []byte, blockSize int) ([]byte, error) {
+	if blockSize <= 0 {
+		return nil, ErrInvalidBlockSize
+	}
+	if len(data)%blockSize != 0 || len(data) == 0 {
+		return nil, ErrInvalidPKCS7Data
+	}
+	c := data[len(data)-1]
+	n := int(c)
+	if n == 0 || n > len(data) {
+		return nil, ErrInvalidPKCS7Padding
+	}
+	for i := 0; i < n; i++ {
+		if data[len(data)-n+i] != c {
+			return nil, ErrInvalidPKCS7Padding
+		}
+	}
+	return data[:len(data)-n], nil
+}
+
+// Decrypt 解密数据
+func (wxa *MiniProgram) Decrypt(sessionKey, encryptedData, iv string) (*UserInfo, error) {
+	aesKey, err := base64.StdEncoding.DecodeString(sessionKey)
+	if err != nil {
+		return nil, err
+	}
+	cipherText, err := base64.StdEncoding.DecodeString(encryptedData)
+	if err != nil {
+		return nil, err
+	}
+	ivBytes, err := base64.StdEncoding.DecodeString(iv)
+	if err != nil {
+		return nil, err
+	}
+	block, err := aes.NewCipher(aesKey)
+	if err != nil {
+		return nil, err
+	}
+	mode := cipher.NewCBCDecrypter(block, ivBytes)
+	mode.CryptBlocks(cipherText, cipherText)
+	cipherText, err = pkcs7Unpad(cipherText, block.BlockSize())
+	if err != nil {
+		return nil, err
+	}
+	var userInfo UserInfo
+	err = json.Unmarshal(cipherText, &userInfo)
+	if err != nil {
+		return nil, err
+	}
+	if userInfo.Watermark.AppID != wxa.AppID {
+		return nil, ErrAppIDNotMatch
+	}
+	return &userInfo, nil
+}