To recognize the effect mechanism of declined reservoir water level on residual soil slope,based on saturated unsaturated seepage theory and unsaturated soil mechanics,the distribution features of seepage field,stress field and displacement field with declined reservoir water level were discussed by using finite element method.The results indicated t hat different declined rates caused different saturated line in the sub grade in the process of reservoir water declining,however,the saturated lines tended to be consistent as time went on.The pore water pressure and the displacement increased with the duration time of water level and declined rate,and the effective stress in the slope increased while the total stress kept constant.The slope safety factor appeared to decrease firstly and increase subsequently.Hence,controlling flood rate and strengthening sub grade drainage in the management of reservoir floor discharge are recommended to benefit reservoir slope stability.