diff --git a/Storage/Storage.Test/GeoTest.cs b/Storage/Storage.Test/GeoTest.cs
new file mode 100644
index 0000000..64eacdf
--- /dev/null
+++ b/Storage/Storage.Test/GeoTest.cs
@@ -0,0 +1,23 @@
+using NUnit.Framework;
+using LeanCloud.Storage;
+
+namespace LeanCloud.Test {
+    public class GeoTest {
+        [Test]
+        public void Calculate() {
+            LCGeoPoint p1 = new LCGeoPoint(20.0059, 110.3665);
+            LCGeoPoint p2 = new LCGeoPoint(20.0353, 110.3645);
+            double kilometers = p1.KilometersTo(p2);
+            TestContext.WriteLine(kilometers);
+            Assert.Less(kilometers - 3.275, 0.01);
+
+            double miles = p1.MilesTo(p2);
+            TestContext.WriteLine(miles);
+            Assert.Less(miles - 2.035, 0.01);
+
+            double radians = p1.RadiansTo(p2);
+            TestContext.WriteLine(radians);
+            Assert.Less(radians - 0.0005, 0.0001);
+        }
+    }
+}
diff --git a/Storage/Storage/LCGeoPoint.cs b/Storage/Storage/LCGeoPoint.cs
index dd5c103..4e1cc39 100644
--- a/Storage/Storage/LCGeoPoint.cs
+++ b/Storage/Storage/LCGeoPoint.cs
@@ -72,7 +72,7 @@ namespace LeanCloud.Storage {
             double a = sinDeltaLatDiv2 * sinDeltaLatDiv2 +
                 Math.Cos(lat1rad) * Math.Cos(lat2rad) * sinDeltaLongDiv2 * sinDeltaLongDiv2;
             a = Math.Min(1.0, a);
-            return 2 * Math.Cos(Math.Sqrt(a));
+            return 2 * Math.Sin(Math.Sqrt(a));
         }
     }
 }