In this paper，seismicity and focal mechanism of the reservoir area after the impoundment are studied by using the data of seismic network of Jinsha River low reaches． In the segments A and B of the reservoir head region seismic activity was staying with low frequency and strength in more than one year since the impoundment． While a significant increase of seismicity in segment C had the largest earthquake with M3.0，which was correlating with the second stage impounding but not the initial impoundment period． The region of seismicity increase is near the Yiziba fault and the middle segment of the Manao fault． Most of earthquakes in these regions are reverse and normal rupture according to focal mechanisms，in which tectonic earthquake takes a large proportion while the rest are reservoir induced and Karst collapse． The result will provide detailed information and example for future reservoir induced earthquake study and forecast．