Reliability analysis of slope stability is essentially a system reliability problem. The traditional reliability calculation method of slope system based on limit equilibrium adopts the safety factor expression as the performance function. The safety factor needs to be solved iteratively, so it is difficult to balance the calculation accuracy and efficiency. Moreover, it is generally assumed that the sliding surface is circular, which is inconsistent with the actual situation. Based on the rigorous limit equilibrium method by modifying normal stress over slip surface, the performance function expressed by critical horizontal acceleration coefficient Kc is established. A slope system reliability calculation method coupling Rosenblueth sampling point method, global critical sliding field method and sequential combination method is proposed. The accuracy and high efficiency of the proposed method are verified by two slope examples. This method can be used as a powerful tool for rapid assessment of slope stability reliability in practical engineering.