Abstract：On May 12, 2:28 pm, an earthquake (Ms 8.0) struck the Longmenshan area (centred in Wenchuan County of Sichuan Province), the eastern segment of the Tibetan Plateau. According to the field survey, the earthquake occurs on the NE striking Longmenshan fault belt. The belt has been with the thrusting rate smaller than 1 mm/a and the shortening rate smaller than 3 mm/a according to GPS measurement. The causative mechanism is mainly the thrust (from NW to SE), accompanied with dextral strike-slip. The earthquake produced several co-seismic surface rupture zones that were 275 km long and 15 km wide in general. The Yingxiu-Beichuan rupture zone is 275 km long and dominative；The Hanwang rupture zone takes the second place, which is 70 km long and occurs along the south part of the Guanxian-Anxian fault, the frontal fault of the Longmenshan fault belt. There are another two minor rupture zones between two zones mentioned above, one is the Shenxigou rupture zone, is in NE direction and about 10 km long, close to the southern segment of the main rupture zone, whose deformation characteristics are similar to and can be involved into the Yingxiu-Beichuan rupture zone; the other is named as Xiaoyudong rupture zone, is in NW direction and 6 km long, produced by the thrust from SW to NE and associated lateral slip, which is the link between Yingxiu-Beichuan and Hanwang rupture zone and characterized by the lateral ramp. Besides, in the Sichuan Basin that eastern to the Guanxian-Anxian fault, a sand liquefaction belt with NE direction strike developed from Juyuan town of Dujiangyan to Jiangyou, which might be the result of the activity of a blind fault deep in the western Sichuan Basin. According to the feature of surface coseismic rupture zones, active tectonics in the Longmenshan fault belt have intense thrusting accompanied with significant dextral strike-slip. The fault is developing toward the Sichuan Basin. The recurrence intervals of great earthquake such as the Wenchuan earthquake can be 3000-6000 years.