Abstract：As widespread usage in engineering，the simplified Bishop method is used to establish the limit state function. Considering the unit weight，cohesive strength and internal friction angle as random variable，the utility optimal method as well as the Microsoft Excel¢s solver are applied to solve the reliability index，which can avoid the problems of orthogonal transformation and derivation of the limit state function. For the slope of granite residual sandy clay in Fujian Province，the reliability analysis is carried out. By comparison the results of non-correlation and correlation between parameters，it is shown that the reliability correlates with not only the mean value of parameters，but also the coefficient of variability and the correlation between parameters which have a major influence on it. Thus，there is a possibility of instability while the slope is considered as stability by the traditional safety factor calculation method.
