Basing on the GPS and precise leveling observation data before and after Wenchuan earthquake 2008, the authors got its co-seismic displacements fields. Combining the field geological investigation, the authors inversed the geometric model of co-seismic fault and slip distribution on the fault plane. The results show that Beichuan-Yingxiu fault is a listric fault with a length of 180 km, the dip on the ground is 62~ and decreases gradually in exponential function along with the depth increase. The maximum slip of the fault model is 7.6 m, which is corresponding to Beichuan area in most severe damage. The seismic moment releasing of Wenchuan earthquake2008 is estimated to be 7.62×1020 N·m, and its corresponding moment magnitude is MW7.9. The geometric model of co-seismic fault is well fit for GPS and precise leveling observation data.