We computed source parameters for 143 earthquakes with M_L≥ 1. 0 occurring from January,2011 to March,2014 using waveform data recorded by the Nuozhadu and Jinghong Reservoir Seismic Networks. Then,the variation of seismic activity and the characteristics of source parameters before and after the impoundment of the reservoir were investigated. The results show that:( 1) the seismic activity increased obviously after the impoundment,especially during the 3- 4 months after impoundment;( 2) the focal depths of the earthquakes occurring in the reservoir area are shallower than the earthquakes occurring outside the reservoir area in the initial stage of impoundment,but after a time,the difference was gradually reduced;( 3) corner frequency varies with the seismic moment and the log-linear relationship is more obvious after impounding;( 4)stress drop and apparent stress increase with increasing seismic moment,moreover they are lower for the earthquakes occurring in the reservoir area after impounding than those occurring outside the reservoir area or before impounding with the same seismic moment;( 5) the effect of reservoir impoundment on an earthquake can reach a depth of 10 km,and the maximum effect is seen at a depth of 3km- 6km,and the differences of seismic activity and average apparent stress between the inside and outside of the reservoir are significant. We computed source parameters for 143 earthquakes with M_L ≥ 1. 0 occurring from January, 2011 to March, 2014 using waveform data recorded by the Nuozhadu and Jinghong Reservoir Seismic Networks. Then, the variation of seismic activity and the characteristics of source parameters before and after the impoundment of the reservoir were investigated. The results show that :( 1) the seismic activity increased obviously after the impoundment, especially during the 3- 4 months after impoundment; (2) the focal depths of the earthquakes occurring in the reservoir area are shallower than the earthquakes occurring outside the reservoir area in the initial stage of impoundment, but after a time, the difference was gradually reduced; (3) corner frequency varies with the seismic moment and the log-linear relationship is more obvious after impounding; (4) stress drop and apparent stress increase with increasing seismic moment, moreover they are lower for the earthquakes occurring in the reservoir area after impounding than those occurring outside the reservoir area or before impounding with the same seismic moment; (5) the effect of reservoir impoundment on an earthquake can reach a depth of 10 km, and the maximum effect was seen at a depth of 3km- 6km, and the differences of seismic activity and average apparent stress between the inside and outside of the reservoir are significant.