On the 20th of April 2013, Lushan Ms7. 0 earthquake occurred in southwest Longmenshan fault which is the boundary of Qingzang block and South China block. In this study, firstly, using double difference algorithm, the locations of main shock (30.29°N, 102.97°E, 17.82 km) and about more than 4100 aftershocks are obtained. Secondly, using seismic waveforms from GSN/IRIS and Sichuan province digital seismic network the focal mechanisms of the main shock and some aftershocks of Ms〉3.0 are determined. According to the focal mechanism and relocation results, the main shock is a thrust type earthquake, and the strike of the fault plane is 200°. Finally, based on the orientation and slip direction of the fault plane solutions and using mechanism axis tensor method, the direction of the mean stress field is obtained.