diff --git a/index.js b/index.js
index 5c153db..4e32a84 100644
--- a/index.js
+++ b/index.js
@@ -144,10 +144,52 @@
     return !(lng > 73.66 && lng < 135.05 && lat > 3.86 && lat < 53.55);
   };
 
+  /**
+   * 坐标系转换
+   * @param {number} lng 经度
+   * @param {number} lat 纬度
+   * @param {'wgs84'|'bd09'|'gcj02'} from 来源坐标系名称
+   * @param {'wgs84'|'bd09'|'gcj02'} to 输出坐标系名称
+   * @returns {[number,number]} [lng,lat]
+   */
+  function convert(lng, lat, from = 'gcj02', to = 'gcj02') {
+      let point = [lng, lat];
+      let arr = {
+          'wgs84': {
+              from: (lng, lat) => wgs84togcj02(lng, lat),
+              to: (lng, lat) => gcj02towgs84(lng, lat)
+          },
+          'bd09': {
+              from: (lng, lat) => bd09togcj02(lng, lat),
+              to: (lng, lat) => gcj02tobd09(lng, lat)
+          },
+          'gcj02': {
+              from: (lng, lat) => [lng, lat],
+              to: (lng, lat) => [lng, lat],
+          }
+      }
+      if (!arr[to]) {
+          console.error('错误的 to 坐标系：' + to);
+          return point;
+      }
+      if (!arr[from]) {
+          console.error('错误的 from 坐标系：' + from);
+          return point;
+      }
+
+      if (to == from) {
+          return point
+      }
+      let temp = arr[from].from(lng, lat);
+      temp = arr[to].to(temp[0], temp[1]);
+      return temp;
+  };
+
   return {
     bd09togcj02: bd09togcj02,
     gcj02tobd09: gcj02tobd09,
     wgs84togcj02: wgs84togcj02,
-    gcj02towgs84: gcj02towgs84
+    gcj02towgs84: gcj02towgs84,
+    convert:convert
   }
 }));
diff --git a/test/app.js b/test/app.js
index 0dcd2ef..bc0d96a 100644
--- a/test/app.js
+++ b/test/app.js
@@ -15,6 +15,18 @@ console.log(bd09togcj02);
 console.log(gcj02tobd09);
 console.log(wgs84togcj02);
 console.log(gcj02towgs84);
+//百度经纬度坐标转国测局坐标
+bd09togcj02 = coordtransform.convert(116.404, 39.915,'bd09','gcj02');
+//国测局坐标转百度经纬度坐标
+gcj02tobd09 = coordtransform.convert(116.404, 39.915,'gcj02','bd09');
+//wgs84转国测局坐标
+wgs84togcj02 = coordtransform.convert(116.404, 39.915,'wgs84','gcj02');
+//国测局坐标转wgs84坐标
+gcj02towgs84 = coordtransform.convert(116.404, 39.915,'gcj02','wgs84');
+console.log(bd09togcj02);
+console.log(gcj02tobd09);
+console.log(wgs84togcj02);
+console.log(gcj02towgs84);
 //result
 //bd09togcj02:   [ 116.39762729119315, 39.90865673957631 ]
 //gcj02tobd09:   [ 116.41036949371029, 39.92133699351021 ]
diff --git a/test/index.html b/test/index.html
index e7cc7bd..933c6e4 100644
--- a/test/index.html
+++ b/test/index.html
@@ -21,6 +21,18 @@ <h1>请按F12打开控制台查看结果！(Please open console by F12！)</h1>
     console.log(gcj02tobd09);
     console.log(wgs84togcj02);
     console.log(gcj02towgs84);
+    //百度经纬度坐标转国测局坐标
+    bd09togcj02 = coordtransform.convert(116.404, 39.915,'bd09','gcj02');
+    //国测局坐标转百度经纬度坐标
+    gcj02tobd09 = coordtransform.convert(116.404, 39.915,'gcj02','bd09');
+    //wgs84转国测局坐标
+    wgs84togcj02 = coordtransform.convert(116.404, 39.915,'wgs84','gcj02');
+    //国测局坐标转wgs84坐标
+    gcj02towgs84 = coordtransform.convert(116.404, 39.915,'gcj02','wgs84');
+    console.log(bd09togcj02);
+    console.log(gcj02tobd09);
+    console.log(wgs84togcj02);
+    console.log(gcj02towgs84);
     //result
     //bd09togcj02:   [ 116.39762729119315, 39.90865673957631 ]
     //gcj02tobd09:   [ 116.41036949371029, 39.92133699351021 ]