diff --git a/slice.go b/slice.go
new file mode 100644
index 0000000..6627ebb
--- /dev/null
+++ b/slice.go
@@ -0,0 +1,56 @@
+/*
+ * string functions
+ */
+package helper
+
+// 求差集
+func Diff(slice1, slice2 []string) []string {
+	m := make(map[string]int)
+	nn := make([]string, 0)
+	inter := Intersect(slice1, slice2)
+	for _, v := range inter {
+		m[v]++
+	}
+
+	for _, value := range slice1 {
+		times, _ := m[value]
+		if times == 0 {
+			nn = append(nn, value)
+		}
+	}
+	return nn
+}
+
+// 求交集
+func Intersect(slice1, slice2 []string) []string {
+	m := make(map[string]int)
+	nn := make([]string, 0)
+	for _, v := range slice1 {
+		m[v]++
+	}
+
+	for _, v := range slice2 {
+		times, _ := m[v]
+		if times == 1 {
+			nn = append(nn, v)
+		}
+	}
+	return nn
+}
+
+// 求并集
+func Union(slice1, slice2 []string) []string {
+	m := make(map[string]int)
+	for _, v := range slice1 {
+		m[v]++
+	}
+
+	for _, v := range slice2 {
+		times, _ := m[v]
+		if times == 0 {
+			slice1 = append(slice1, v)
+		}
+	}
+	return slice1
+
+}
diff --git a/slice_test.go b/slice_test.go
new file mode 100644
index 0000000..9217c1b
--- /dev/null
+++ b/slice_test.go
@@ -0,0 +1,27 @@
+package helper
+
+import (
+	"fmt"
+	"testing"
+)
+
+func Test_Diff(t *testing.T) {
+	var aa = []string{"43", "33"}
+	var bb = []string{"2", "33", "1"}
+	cc := Diff(aa, bb)
+	fmt.Println(cc)
+}
+
+func Test_Intersect(t *testing.T) {
+	var aa = []string{"43", "33"}
+	var bb = []string{"2", "33", "1"}
+	cc := Intersect(aa, bb)
+	fmt.Println(cc)
+}
+
+func Test_Union(t *testing.T) {
+	var aa = []string{"43", "33"}
+	var bb = []string{"2", "33", "1"}
+	cc := Union(aa, bb)
+	fmt.Println(cc)
+}