The invention provides a failure running method and device of a redox flow battery system. The failure running method comprises the steps of judging whether a failure redox flow battery system requires an isolation electric stack part or not when that the redox flow battery system is failure is determined; reducing a charge-discharge power of the redox flow battery system according to a preset failure running strategy if the isolation electric stack part is not needed, running the redox flow battery system according to a power reduction class running mode, and maintaining the energy response capability of the system; and improving the charge-discharge power of the redox flow battery system according to the preset failure running strategy if the isolation electric stack part is needed, running the redox flow battery system according to a power multiplying class running mode, isolating a failure electric stack part in a redox flow battery, improving a power of a normal power unit, and maintaining the power response capability of the system. With the technical scheme provided by the invention, the reliability of the running mode taken by an all-vanadium redox flow battery system under a failure condition can be effectively and quantitatively analyzed, and the reliability of the redox flow battery system can be effectively evaluated.