diff --git a/strings.go b/strings.go
index 79bf89b..f2860a5 100644
--- a/strings.go
+++ b/strings.go
@@ -307,13 +307,39 @@ func Reverse(s string) string {
 	return B2S(b)
 }
 
-// IsNumeric 检查字符串是否全是数字: 0-9
+// IsNumeric 检查字符串是否全是 ASCII 数字: 0-9
 func IsNumeric(s string) bool {
 	if s == "" {
 		return false
 	}
-	for _, char := range s {
-		if char < '0' || char > '9' {
+	for _, c := range s {
+		if c < '0' || c > '9' {
+			return false
+		}
+	}
+	return true
+}
+
+// IsLetter 检查字符串是否全是 ASCII 字母
+func IsLetter(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z') {
+			return false
+		}
+	}
+	return true
+}
+
+// IsLetterOrNumeric 检查字符串是否全是 ASCII 字母或数字
+func IsLetterOrNumeric(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9') {
 			return false
 		}
 	}
diff --git a/strings_test.go b/strings_test.go
index 6e39ce5..37fa462 100644
--- a/strings_test.go
+++ b/strings_test.go
@@ -552,8 +552,8 @@ func TestSubString(t *testing.T) {
 func TestIsNumeric(t *testing.T) {
 	t.Parallel()
 	for _, tt := range []struct {
-		s         string
-		isNumeric bool
+		s   string
+		res bool
 	}{
 		{"", false},
 		{" 123", false},
@@ -564,7 +564,44 @@ func TestIsNumeric(t *testing.T) {
 		{"1234567890777", true},
 		{"0", true},
 	} {
-		assert.Equal(t, tt.isNumeric, IsNumeric(tt.s))
+		assert.Equal(t, tt.res, IsNumeric(tt.s))
+	}
+}
+
+func TestIsLetter(t *testing.T) {
+	t.Parallel()
+	for _, tt := range []struct {
+		s   string
+		res bool
+	}{
+		{"", false},
+		{" Abc", false},
+		{"A bc", false},
+		{"Hello123", false},
+
+		{"aBc", true},
+		{"z", true},
+	} {
+		assert.Equal(t, tt.res, IsLetter(tt.s))
+	}
+}
+
+func TestIsLetterOrNumeric(t *testing.T) {
+	t.Parallel()
+	for _, tt := range []struct {
+		s   string
+		res bool
+	}{
+		{"", false},
+		{" Abc", false},
+		{"A 12", false},
+
+		{"Hello123", true},
+		{"aBc", true},
+		{"1230", true},
+		{"z", true},
+	} {
+		assert.Equal(t, tt.res, IsLetterOrNumeric(tt.s), tt.s)
 	}
 }