Abstract: Kezhi’er reservoir is a large hydro project built on the active fault and strong earthquake region with10years construction. The reservoir has been operating for 10 years, the maximum water level is up to 1148.3 m near to the maximum profitable water level of 1149.6 m. The dam experienced the trials of 5.6M earthquake with18 km apart from epicenter occurred on15th May, 1999 and 50-year return flood with peak flow of 2590m3 /s occurred on23rd July,1999. No abnormal event has been found in dam by inspecting after earthquake and analysing observational data. The part defects resulted from foundation treatment and constructing quality in construction period.