Abstract: This paper focused on the influences on the seismic activity and the crustal stress caused by three water storages in Jinping hydro-power station, according to the seismic activity in Jinping hydro-power station and the change of shear-wave splitting parameters of the station MLI from January 2012 to December 2013 . The results show that, after three water storages, the seismic activity in this region continued to increase, especially after the second water storage, and finally remained at a high level. Moreover, the polarization direction of fast shear-wave at the seismic station MLI also showed significant changes before and after three water storages of the hydro-power station. Before the water storage of Jinping hydro-power station, the predominant polarization direction at MLI seismic station was northeast, which was in agreement with the strike of Jinpingshan-Xiaojinhe fault. After the first storage, the polarization directions are distributed scatteredly. After the second water storage, the predominant polarization direction changed to southeast. And the polarization directions showed the southeast consistently after the third water storage. As for the station MLI, the delay time of slow shear-wave has changed before and after the three storages of Jinping hydro-power station, especially after the second storage the delay time of slow shear-wave decreased obviously. Thus, the seismic activity, the polarization directions of fast shear-wave and the delay time of slow shear-wave changed significantly after the second water storage of Jinping hydro-power station, suggesting that the direction of crustal stress changed quickly in a small region after the second water storage, and the crustal stress also released with the enhanced seismic activity.