The genesis and mechanism of Wenchuan great earthquake are discussed agai.Based on the speech of some people who escaped by the earthquake in the epicentral area,Wenchuan earthquake was caused by deep gas protruding and explosion.The viewpoint mentioned above was proved by some other investigation and survey such as anomolies of satellite thermo-infrared surving and some macroscopic anormalies before the earthquake.The viewpoint of the relationship between earthquake and gas by some scholars in abroad and in home should be deeply concerned.