A trailer motor control method comprises: acquiring a vehicle status signal; determining, according to the vehicle status signal and/or a derivative signal thereof, a vehicle operating mode; and determining, at least according to the vehicle operating mode and the vehicle status signal, a torque value outputted by a trailer motor (145). A trailer can provide a suitable auxiliary torque at the right time according to changes in operation conditions of a running vehicle, thus achieving high control accuracy and improved robustness. The method imposes no restrictions on the power type, brand, and model of tractors and trailers, and allows a random combination therebetween.