The analysis of structural plane in rock slope is of vital importance to stability analysis of rock slope. In this paper, Bayesian method was adopted in the analysis of shear strength parameters along the fault in the West Slope of Upper Reservoir, Shisanling Pumped Storage Power Station. Full advantage was taken of the geological information outside the structural plane along with the practical experience of on-site engineers. The statistical estimation problem of small samples thus was successfully solved. The determination of sliding plane in rock slope is another key issue in the stability analysis of rock slope. The cracking process was utilized to track the most possible sliding plane in the slope. In consideration of the randomicity of both mechanical parameters of rock and structural plane and resistance of slide resistant piles, reliability index of slope stability was established with the aid of discretized dimensional reduction method of reliability and conditional probability.