Abstract: Using both absolute arrival time, relative arrival time and waveform correlation data of Nuozhadu reservoir earthquake events, we obtained seismic relocation and 3D P wave velocity structure of three periods by double-difference seismic tomography method. The results show that after the reservoir impoundment, a large number of earthquakes occurred at the reservoir area, and the aftershocks after relocation is mostly located at the depth within 10 km, especially in the range of less than 5 km, which is basically consistent with the previous result that the depth of reservoir-induced earthquake is less than 10 km. With the increase of water storage, the reservoir water penetrates along the fault, the pore pressure changes, which causes earthquakes-increased-area to extend to the Heihe river and the middle part of the Lancangjiang river, and further to the Weiyuanjiang and the Xiaoheijiang rivers. The P wave velocity in these regions is reduced. The maximum depth of the overall reservoir seepage is less than 7 km.