The first drilling hole of the Wenchuan earthquake fault science drilling project (WFSD-1) experienced up to more than 30 meters of the fault gouge drilling process. According to the research and application, the drilling mud system with high density, low water loss, low permeability, lubrication and resistance reducing was formed, and together with the equilibration by ground stress, coring in fault gouge was successfully made, which was the basis of the successful completion of the first hole construction in the Wenchuan earthquake fault scientific drilling.