The material parameters and geometric parameters of wedge slopes have high variability， and there are several failure modes for a wedge slope. It is necessary to carry out system reliability analysis for wedge slopes. We consider a wedge slope as a series system which is composed of four failure modes， and we consider each failure mode as a parallel sub-system with three components. Then， the reliability analysis is carried out by using the product of conditional marginal method and bound method of system reliability analysis. A new method for the linearization of nonlinear performance function is proposed for computing the coefficient of correlation between each failure modes in the parallel sub-system. Through the reliability analysis of a wedge slope， it is illustrated that a wedge slope can be considered as a series-parallel system， and the new linearization method can simulate the failure domain accurately. The failure modes computed from the reliability analysis and the deterministic method is different. Reliability analysis method is suitable for the design and management of wedge slopes.