diff --git a/README.md b/README.md
index 247309d..56ce3dc 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,8 @@ clop (Command Line Option Parse)是一款基于struct的命令行解析器，麻
 		- [Parsing flag code to generate clop code](#Parsing-flag-code-to-generate-clop-code)
 - [Implementing linux command options](#Implementing-linux-command-options)
 	- [cat](#cat)
+- [faq](#faq)
+	- [The subcommand or option does not take effect](#The-subcommand-or-option-does-not-take-effect)
 
 ## Installation
 
@@ -708,3 +710,8 @@ Args:
     <files>
 */
 ```
+
+## faq
+### The subcommand or option does not take effect
+q: 关于子命令或者命令行命令没有生效  
+a: 可以检查下结构体的字段是否是大写开头。
\ No newline at end of file
diff --git a/clop.go b/clop.go
index 8b76ecb..be4ab3c 100644
--- a/clop.go
+++ b/clop.go
@@ -15,7 +15,7 @@ import (
 var (
 	ErrDuplicateOptions = errors.New("is already in use")
 	//ErrUsageEmpty       = errors.New("usage cannot be empty")
-	ErrUnsupported  = errors.New("unsupported command")
+	ErrUnsupported  = errors.New("unsupported clop command")
 	ErrNotFoundName = errors.New("no command line options found")
 	ErrOptionName   = errors.New("Illegal option name")
 )
@@ -841,7 +841,7 @@ func (c *Clop) parseTagAndSetOption(clop string, usage string, def string, field
 			c.envAndArgs = append(c.envAndArgs, option)
 
 		default:
-			return fmt.Errorf("%s:(%s) clop(%s)", ErrUnsupported, opt, clop)
+			return fmt.Errorf(`%s:(%s) clop:"%s", Maybe you need to clop:"short;long"`, ErrUnsupported, opt, clop)
 		}
 
 		if strings.HasPrefix(opt, "-") && len(name) == 0 {
diff --git a/clop_usage_must_have_value_test.go b/clop_usage_must_have_value_test.go
index 9086e13..0dea07b 100644
--- a/clop_usage_must_have_value_test.go
+++ b/clop_usage_must_have_value_test.go
@@ -8,7 +8,10 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func Test_Issue(t *testing.T) {
+// 该文件定位
+// 各种出错的提示信息自测函数
+
+func Test_Usage_MustHaveValue(t *testing.T) {
 
 	type test struct {
 		Long int `clop:"short;long" valid:"required"`
@@ -36,3 +39,15 @@ func Test_Issue(t *testing.T) {
 		assert.NotEqual(t, strings.Index(tc, "must have a value!"), -1)
 	}
 }
+
+func Test_Usage_UnknownCommand(t *testing.T) {
+	type cmd struct {
+		C string `clop:"C" usage:""`
+	}
+
+	c0 := cmd{}
+	var b bytes.Buffer
+	c := New([]string{}).SetOutput(&b).SetExit(false)
+	c.Bind(&c0)
+	assert.NotEqual(t, strings.Index(b.String(), `clop:"short;long"`), -1)
+}