Abstract: In order to study the influence of rainfall on stability of Taiping dam in Liangshan，the SEEP/Win Geostudio is used to establish a seepage field. After setting the parameters in rock or seepage with 10 years, 25 years, 50 and 100 years as a point of rainfall respectively, slope stability analysis under different rainfall durations is carried out to obtain relation curve of rainfall intensity ,rainfall duration and dam stability. The results show that when rainfall durations are longer, dam safety factor becomes lower and the gathering at the foot of dam can easily lead to negative stability; security forecasting can be made for tailing dam in different rainfall intensity by means of the curve, which is of far-reaching significance.