The invention belongs to the technical field of power and electronic system control, and especially relates to a cooperative control system and method for a railway purifying power device. A technical problem to be solved is to provide the railway purifying power device cooperative control system and method, and the system and method can enable the railway purifying power device to be put in use smoothly and reliably through changing the operation time limit of the relay protection without changing the relay protection rule. The technical scheme of the invention is that the railway purifying power device comprises an output smoothing wave reactor, a voltage support and filter capacitor, a discharge loop, an output isolation transformer, a bus connection circuit breaker, a 27.5kV step-down multi-tap rectifier transformer and a multilevel cascading converter. The system comprises a characteristic slope control module, a single-phase grounding fault control module, a large-current short circuit fault control module and a hard turn-off impact prevention control module. The system and method are suitable for the field of power system control.