According to the requirement of the Unmanned Air Vehicle(UAV) Mission Planning, a new UAV Mission Planning method was designed based on secondary development of Google Earth. At first, Mission Planning messages were received using Planning algorithm. Then, planning track was presented by introducing threat data, planning data and plane data into Google Earth via its extendable interface.System results show that this method not only omit the terrain building but also can generate one Planning track quickly with high fidelity and meet the performance requirement of the UAV.