Abstract: Dextral-slip thrusting of major active faults in Longmenshan Mts. related to eastward extrusion of Songpan-Ganzi terrain in eastern Tibetan Plateau caused the Ms 8.0 Wenchuan Earthquake. Seismic scarps, pressure ridges, seismic fractures and seismic faults formed along Beichuan-Yingxiu fault in central Longmenshan Mts., and extension of seismic zone along Beichuan-Yingxiu fault exceeds 250km. Maximum co-seismic displacements with 6.1m dextral slip, 4.6m vertical displacement and 7.6m total displacement occurred in Yingxiu near the seismic epicenter. Co-seismic dextral slip, vertical displacement and total displacement along Yingxiu-Beichuan fault are respectively 2.7m, 4.6m and 5.3m in Hongkou, 5.7m, 3.4m and 6.6m in Beichuan, and 3.2m, 3.0m and 4.4m in Pingtong. Minor co-seismic displacement (￡1.0m) formed along Hanwang-Xuankou fault in east Longmenshan Mts. and Maoxian-Wenchuan fault and Qingchuan fault in west Longmen Mts. though evident seismic faulting occurred along these active faults. Recurrence interval of Ms 8.0 earthquake in Longmen Mts. is estimated to be 1150-2950 years according to maximum co-seismic displacement and structural convergent rate determined by GPS.