Abstract: GIS and numerical simulation techniques are used to quantitative risk assessment of induced earthquake in the ThreeGorge reservoir head area. The technical route is that the simulation model is set up through the analysis of affecting factors. The simulation result is obtained with FLAC 3D. The assessment database is set up by the result of simulation and monitoring data. Each unit is estimated with the maximum tensile strain criterion for judging rock tensile failure and the MohrCoulomb criterion for judging rock shear failure. The unit is further estimated by comparing the first principal stress,the third principal stress and the displacement where the induced earthquake had taken place after impounding of the reservoir on a GIS platform. The result shows that building database containing various data based on the same GIS platform is the basement of integrated factor model. The result of risk assessment possesses the reliability in the ThreeGorges reservoir head area. The simulation result is also calculated with the earthquake model and the calculated result is further modified with the monitored data．