///The study area, Songpan-Ganzi region, lies in the northeast corner of the Qinghai-Tibet plateau. Totally 993 earthquake faults with various properties are distinguished by statistic analysis based on 4781 observed faults longer than 2 km in 1 to 200 000 scale and 5 220 seismic records since 1900, and field investigation data, that allows to establish a centennial seismotectonic framework in the study area. The relationship between the seismicity and the fault movement was dominantly controlled by a transpressional shearing and showing a typical wedge effect. The condition of the Wenchuan 8.0 earthquake nucleation is accumulated by an increase of velocity vector components vertical to the fault plane, since the trend of the Xianshuihe fault is sharply southward bending at its mid and southeast segment, which also caused the earthquake fractures running northeastwards from the epicenter.