The invention provides a power system fault diagnosis method allowing warning information uncertainty to be considered, and relates to a power system fault diagnosis method. At present, when faults occur, protective relays and circuit breakers are likely to operate mistakenly or reject operation, untimely uploading or distortion or missing or other situations are likely to occur in an alarm uploading process, and accurate diagnosis results cannot be obtained. The power system fault diagnosis method comprises the following steps that 1) according to protective-relay action information, circuit-breaker action information and static power grid topological data after the faults occur, power-outage regions before and after the faults are formed, and fault regions are identified automatically; 2) protective-relay configuration information is combined, information content loss is calculated in an information content loss algorithm during fault diagnosis, an objective function is formed, and a fault diagnosis model is built; 3) the fault diagnosis model is solved in a genetic algorithm, failure equipment is obtained, and actions of the protective relays and the circuit breakers are evaluated. According to the technical scheme, the power system fault diagnosis method has good fault tolerance and meanwhile can give various possible fault combinations and the occurrence probability of the corresponding fault combinations.