diff --git a/core-xhr.html b/core-xhr.html
index ea22804..8415606 100644
--- a/core-xhr.html
+++ b/core-xhr.html
@@ -71,21 +71,36 @@
         }
         return xhr;
       },
-    
+
       toQueryString: function(params) {
+        var r = this.encodeObject(params, '');
+        return r.join('&');
+      },
+
+      encodeKeyValuePair : function(n, v){
+        return v == null ? n : (n + '=' + encodeURIComponent(v));
+      },
+
+      encodeObject : function(obj, prefix){
         var r = [];
-        for (var n in params) {
-          var v = params[n];
-          n = encodeURIComponent(n);
-          r.push(v == null ? n : (n + '=' + encodeURIComponent(v)));
+        prefix = prefix || '';
+        for (var n in obj) {
+          var v = obj[n];
+          if(typeof v === 'object') {
+            n = prefix + encodeURIComponent('[' + n + ']');
+            r = r.concat(this.encodeObject(v, n));
+          } else {
+            n = prefix + encodeURIComponent(prefix ? '[' + n + ']' : n);
+            r.push(this.encodeKeyValuePair(n, v));
+          }
         }
-        return r.join('&');
+        return r;
       },
 
       isBodyMethod: function(method) {
         return this.bodyMethods[(method || '').toUpperCase()];
       },
-      
+
       bodyMethods: {
         POST: 1,
         PUT: 1,
@@ -112,5 +127,5 @@
     });
 
   </script>
-  
+
 </polymer-element>
diff --git a/test/core-ajax.html b/test/core-ajax.html
index ea21f09..7d8689e 100644
--- a/test/core-ajax.html
+++ b/test/core-ajax.html
@@ -280,6 +280,56 @@
         });
       });
     });
+    suite('params', function() {
+      suiteSetup(function () {
+        ajax.url = "http://example.com/";
+      });
+      test('should write single level object param to query string correctly.', function (done) {
+        async.series([
+          function (cb) {
+            ajax.params = '{"s": "bar", "t":"foo"}';
+            ajax.method = 'POST';
+            ajax.body = '';
+            cb();
+          },
+          animationFrameFlush,
+          function (cb) {
+            assert.equal(requests[0].requestBody, 's=bar&t=foo');
+            cb();
+          }
+        ], done);
+      });
+      test('should write 2 level object param to query string correctly.', function (done) {
+        async.series([
+          function (cb) {
+            ajax.params = '{"s": { "t": "bar", "u": "foo"}}';
+            ajax.method = 'POST';
+            ajax.body = '';
+            cb();
+          },
+          animationFrameFlush,
+          function (cb) {
+            assert.equal(requests[0].requestBody, '%5Bs%5D%5Bt%5D=bar&%5Bs%5D%5Bu%5D=foo');
+            cb();
+          }
+        ], done);
+      });
+      test('should write multi level object param to query string correctly.', function (done) {
+        async.series([
+          function (cb) {
+            ajax.params = '{"s": { "t": {"v": "bar" }, "u": "foo"}}';
+            ajax.method = 'POST';
+            ajax.body = '';
+            cb();
+          },
+          animationFrameFlush,
+          function (cb) {
+            assert.equal(requests[0].requestBody, '%5Bs%5D%5Bt%5D%5Bv%5D=bar&%5Bs%5D%5Bu%5D=foo');
+            cb();
+          }
+        ], done);
+      });
+    });
   });
   </script>