The invention provides a circuit system fault-tolerant capability simulation analysis method considering cascade failure. The circuit system fault-tolerant capability simulation analysis method comprises the steps of S1, realizing structure and function analysis; S2, constructing a netlist file; S3, constructing a failure description file; S4, carrying out initial injection failure; S5, calling the SPICE for simulation; S6, judging whether cascade failure occurs or not, if the cascade failure occurs, updating the circuit structure information and returning to the step S2, and if the cascade failure does not occur, considering that the cascade failure process is stopped; S7, collecting relevant data of a cascade failure propagation path; S8, carrying out redundancy backup on the key components according to a cascade failure analysis result in the step S7; and S9, updating the circuit structure, and recalculating the improvement degree of the fault-tolerant capability of the improved anddesigned circuit. Simulation calculation analysis is carried out based on SPICE simulation software, cascade failure propagation behaviors of the circuit system can be analyzed from the perspective of the system, fault-tolerant design of the circuit system is guided, and method support is provided for circuit internal structure optimization and reconstruction.