Abstract: At present,the safety factor of sliding resistance determined by the limit equilibrium method based on the determinate property parameters of soils is used to evaluate the stability of the dam slopes.However,the property parameters of practical soils are variables with in a certain changeable range,so the instability probability of the dam slopes with a larger factor of safety is not always less than that with a less factor of safety.Based on studies on the statistical properties of soil strength parameters of 12 uniform earth dams,using the Monte-Carlo method to perform the dam slope instability probability analysis for the critical slipping surface,the influence of the mean value,variability and correlation of strength parameters of the fill materials of the dams on the instability probability of the dam slopes was studied.The results show that the uncertainty of strength parameters has significant influence on the instability probability of the dam slopes.The instability probability of the dam slopes decreases with the increase of the mean values and increases with the increase of the coefficients of variability of the strength parameters.The correlation between the two strength parameters also has evident influence on the instability probability.Therefore,during the evaluation of the stability of the embankment dam slopes,based on the deterministic analysis,if the uncertainty of strength parameters can be considered and the instability probability of the dam slopes can be calculated,the assessment of dam safety can be more scientific and reasonable.