diff --git a/flag.go b/flag.go
index 22dff76..adc5b9d 100644
--- a/flag.go
+++ b/flag.go
@@ -11,7 +11,7 @@ var (
 )
 
 func dna_flag() {
-	flag.StringVar(&file_output, "o", "a.nex", "files name wait to out")
+	flag.StringVar(&file_output, "o", "a.nex", "output file")
 	flag.Parse()
 	file_input = flag.Args() // []string{"foo", "bar"}
 	fmt.Println("==============")