The invention discloses a motor differential protection system and a motor differential protection method. The system comprises motor protection devices and a neutral-point current collection device, wherein the motor protection devices correspond to one or more motors; the neutral-point current collection device converts the neutral-point current of each motor into digital signals, and sends each group of current signals to the corresponding motor protection device in a communication way; and the motor protection devices collect the end side current of the motors, conduct synchronous processing in combination with signals sent by the neutral-point current collection device so as to fulfill a differential protection function. According to the system and the method, a CT saturation problem caused by an overlong neutral-point current collection cable can be solved, the differential protection performance and the external fault anti-misoperation capability are improved, the reliability of signals is enhanced, on-site wiring can be simplified and the investment can be saved.