Aiming at the seepage of an earth rock dam，reinforcement scheme of inclined clay wall combined with drainage of bank slope is adopted.The seepage and slope stability of the earth rock dam before and after reinforcement are analyzed during stable seepage period and unstable seepage period.The results indicate that compared with earth-rock dam before reinforcement，the seepage discharge and seepage gradient are decreased after reinforcement，the safety factor of upstream slope is increased，and the failure probability of downstream slope is dramatically reduced.The safety factor and failure probability of dam after reinforcement meet standard requirements，which shows that the reinforcement measures adopted are reliable and effective.