Abstract: The triggering fault of Ms 8.0 Wenchuan earthquake on May 12th, 2008 is the Guanxian-Anxian fault, the frontal thrust of the Longmenshan thrust belt, or a newly created fault near the Guanxian-Anxian fault with the similar attitude. The triggering fault is a NE trending, NW dipping and mainly of thrusting with dextral strike slip fault. The Wenchuan earthquake is resulted form the tectonic stress accumulation and release in the frontal fault of Longmenshan thrust belt caused by the SEE ward horizontal compression from the eastern Tibet plateau including the Longmenshan toward the northwest margin of Sichuan basin, and the SEE ward horizontal compression is led by the indentation collision and subducton of India continent against the Tibet plateau after the continent-continent collision 50 Ma B.P., which resulted to the crust movement from NNE to NE to NEE to SEE gradually from middle Tibet to eastern Tibet. The Wenchuan earthquake leds to a tectonic model of uplifting of the eastern margin of Tibet plateau, the Longmenshan Mountians, through the upper crust thrusting and shortening in the Longmenshan thrust belt. That is basically different from Burchfiel's model about the Longmenshan uplifting resulted from the ductile lower crust flow eastwart barred by strong Sichuan basin crust and become upwelling. Probably both models worked in the different stages of the Longmenshan uplifling respetively, but our model is essential because we have seen it worked in the Wenchuan earthquake.