diff --git a/protocol/unit.go b/protocol/unit.go
index b121c7f..156711a 100644
--- a/protocol/unit.go
+++ b/protocol/unit.go
@@ -195,6 +195,7 @@ func getVolume(val uint32) (volume float64) {
 	return
 }
 
+// IsStock 是否是股票,示例sz000001
 func IsStock(code string) bool {
 	if len(code) != 8 {
 		return false
diff --git a/util.go b/util.go
new file mode 100644
index 0000000..7c827bc
--- /dev/null
+++ b/util.go
@@ -0,0 +1,8 @@
+package tdx
+
+import (
+	"github.com/injoyai/tdx/protocol"
+)
+
+// IsStock 是否是股票,示例sz000001
+var IsStock = protocol.IsStock