The invention discloses a photovoltaic power station fault diagnosis method. The method has the advantages that the automatic testing optimization design is achieved, the fault coverage rate of a testing scheme is increased, the fault ambiguity, the average test cost and the average test time are reduced, the test redundancy is designed according to needs, the overall test cost is reduced, and the test time is shortened; a photovoltaic power station fault strategy is automatically generated, online automatic diagnosis of photovoltaic power station faults is achieved, shut-down is avoided in the diagnosis process, the faults are fast and accurate to locate, the harm time of the faults is shortened, the fault shut-down time is shortened, and the power generation time of a photovoltaic power station is prolonged; dependence, on the technical level of personnel, of the photovoltaic power station faults is reduced, the diagnosis cost is low, the diagnosis level is stable, the diagnosis work amount is small, the requirement for test equipment is low, fast maintaining can be achieved, the power generation time is guaranteed, the diagnostic procedure is fast, and therefore further deterioration of the faults is prevented.