Abstract: The origin and distribution of induced earthquakes,associated with the impoundment of the Xinfengjiang reservoir depend not only on the local tectonic environment but also on the additional stress state which is caused by the water loading strain.Therefore,reservoir induced earthquakes tended to be concentrated on the margin of the lake and occurred in two iayers according to the focal depth,between which is a rare-earthquake layer.The frequency of the shallow events has a correlation to the water level of the lake. On the contrary,the earthquakes in the deep layer occurred more often during offset of the lake. In the Xinfengjiang area there are two kinds of seismic faults. Both of them obviously are high angle active faults,which play a much more important role than low angle faults in occurrence of the reservoir induced earthquakes.By means of mathematical simulation to restore the earthquake sequences of this area after impoundment of the lake,it is sure that in the case of certain tectonic stress field,the high angle faults perpendicular to the additional tension stress are more unstable than the others. The calculations also indicate that the seismic events caused by the given geological model in the presence of the stress field with the maximal stress axes striking N30癢,the minimal stress axes striking N30癊 and the moderate stress axes vertical fit in with,the actual earthquakes. The stress fields derived from the calculations are similar to those obtained by other means. Mathematical simulation demonstrats that the NNW-trending fault belt generating the main shock (M=6.1) is the least stale. The seismogenic structures of main shock and two after-shocks with a magnitude greater than 5 belong to the same fault. After the main shock,the stress states for rock changed,and the NNE and ENE faults are less stable.