Abstract: A lot of paddle slopes will be formed after the impoundment of a reservoir.After that due to the permeation of water the inundation volume increases,and it will would lead to the decline of effective stress or sliding resistance and the strength of partial sliding zone.On the other hand,under the drawdown condition of the reservoir,the excess pore pressure will be produced for the sake of the lagged effect of the declining underground water.So the stability of the slopes will be influenced as well.The stability analysis of slopes under the drawdown condition of reservoirs is a new important subject.The achievements of this aspect in recent years were concluded,and a comparison between the analytic and the numerical solutions under the drawdown condition of reservoirs and the inaccuracy of location of phreatic surface determined by the empirical generalization stability analysis were studied.