diff --git a/example/Codes2/main.go b/example/Codes2/main.go
index e78c89d..15861f9 100644
--- a/example/Codes2/main.go
+++ b/example/Codes2/main.go
@@ -2,6 +2,8 @@ package main
 
 import (
 	"fmt"
+	"strings"
+
 	"github.com/injoyai/logs"
 	"github.com/injoyai/tdx"
 )
@@ -13,4 +15,11 @@ func main() {
 	c := cs.Get("sz000001")
 
 	fmt.Println(c.FloatStock, c.TotalStock)
+
+	for _, v := range cs.GetIndexes().Codes() {
+		if strings.HasPrefix(v, "sz") {
+			logs.Debug(v)
+		}
+	}
+
 }
diff --git a/protocol/unit.go b/protocol/unit.go
index 0384c1d..3ed78b0 100644
--- a/protocol/unit.go
+++ b/protocol/unit.go
@@ -302,7 +302,9 @@ func IsIndex(code string) bool {
 	case code[0:2] == ExchangeSH.String() && code[2:5] == "000":
 		return true
 	case code[0:2] == ExchangeSZ.String() && code[2:5] == "399":
+		return true
 	case code[0:2] == ExchangeBJ.String() && code[2:5] == "899":
+		return true
 	}
 	return false
 }