Abstract：The main problem on simulation of tectonic stress field after reservoir impounding in the head area of the Three Gorges is the influence of“canyon effect” and “rock soften”. For the first time，taking the terrain，water load distribution，infiltration range and the fault units into account，the 3D numerical modeling of the upper crust of the Head Area of the Three Gorges is established on the software platform of Marc to reflect the change of tectonic stress field under the load cases—water lever 175 m and 135 m. From the numerical simulation results，it is discovered that under water level 135 m，the maximum principal stress descends(3.5-5.0 MPa) is connected with the activities of high angle normal fault and these changes are more obvious under water level 175 m. The idea of“secondary induced earthquake”，“potential induced seismic source in reservoir”and “superposition seismic source”are presented first. Moreover，the effects on the stability of area fault and the seismogenic environment in Zhigui and Badong after impoundment are analyzed.
