The invention discloses a supplementing electrical control method for safety protection of a gantry crane. A gantry crane alarm, a fence door electromagnetic lock, a first button switch, a second button switch, a circuit breaker, a cross-shaped limiting sensor, a first limiting switch, a second limiting switch, a wireless signal transmitter, a wireless signal receiver, an integrated controller, a first relay, a second relay, a third relay, a fourth relay and a passing alarm lamp are used in the supplementing electrical control method. All of the electrical components except the fence door electromagnetic lock and the wireless signal receiver are connected to a control circuit. Automatic alarming of the gantry crane alarm can be achieved, and constructors are prompted to pay attention to avoiding. When the gantry crane runs to the range within five meters of a vertical shaft, the fence door electromagnetic lock can be controlled to be locked, it is ensured that the constructors cannot enter a fence door, and favorable conditions are provided for construction safety. When the fence door is opened, it is shown that the constructors pass below the vertical shaft, the gantry crane is controlled to be forbidden to run towards the vertical shaft area, and the construction safety of the constructors is ensured.