The present application discloses a method and a system for relay diagnosis. The method includes: transmitting a control signal to the relay, wherein types of the control signal include an enable signal and a disable signal; applying a detection signal at one side of the relay, and receiving a feedback signal at the other side of the relay; and comparing the detection signal with the feedback signal to obtain a comparison result, wherein if the comparison result matches the control signal, the relay is determined as being normal, otherwise, the relay is determined as fault. The present application simply needs to concern whether the relay being diagnosed is enabled or not, and compares the received feedback signal with the applied detection signal to realize the relay diagnosis, thereby avoiding the impacts from other devices in the relay circuit. Thus, the diagnostic efficiency and accuracy can be improved.