Aiming at the problem of speed synchronization accuracy of gantry dual-drive system,a speed tracking synchronous coupling control method was proposed.In order to realize accurate tracking of external loads,a sliding mode load observer based on Sigmoid function was constructed;a dual-motor mean-value synchronous difference controller combined with an integral sliding mode was designed,and a tracking error backstepping controller was combined to formulate a coupled control strategy of speed synchronization error and tracking error,and simulation tests were completed for two load cases.The simulation results show that compared with the PID control,the coupled control strategy reduces the synchronization error by 52.4% and the response time by 75%;compared with the single backstepping control,the coupled control strategy reduces the synchronization error by 39.1% and the response time by 17%.