Abstract: Earthquake monitoring in reservoir head region of TGP started 46 years ago,which is rare in the hydraulic electricity history all over the world. The synthetic analysis for all of the earthquake monitoring data indicates that before the reservoir retained water, reservoir head region was a typical weak earthquake region in which earthquake did not happen frequently, and the intensity of the earthquake was low. Its epicenter primarily located in east side and west side of the Zigui Basin, It mostly belonged to the natural tectonic earthquake respecting the cause. After retaining water, the frequency of seismicity increases significantly, the strength keeps in its background level before retaining water, the strongest earthquake is only ML2.4. The space location of the seismicity has changed greatly after retaining water, the seismicity primarily locates in reservoir region from Niukou in Badong to Peishi in Wushan.?