According to the migration characteristics of three main shocks of the Long ling earthquake from the south to the north and the temporal-spacial zoning characteristics of sources based on the seismic activities of three main shocks and strong after shocks, the authors consider that the seismic type of the Longling earthquake is belong to a type of great ensuing earthquakes, i.e. the three main shocks are located on different sources respectively which link each other from the beginning and the end, and the three source regions have its fore-and after-shocks respectively. The reason why the Longling earthquake occurred in complete granite has been interpreted by stereo model and shear creep fault in deep, It has also been explained, forming multiple source when the main shock occurred and developing aftershocks because of the relative complete medium and the strong regional compress stress. A method to estimate magnitude of multiple source summing the length of each source fault has been advanced.