In order to improved the speed control performance of the tractor motor and system’s antidisturbance as well as the robustness to the parameter change, the PI control strategy of the control system was replaced by the integral sliding mode control strategy. Aiming at load changes in the running process of the electric locomotive, the load torque observer was designed to observe the load torque in realtime, the observed value was integrated into the control strategy and improved the speed of the load mutation control. It could also improve the dynamic and static characteristics of traction motor. Simulation experiments showed that the load observer could quickly and accurately follow the load changes. The sliding mode speed controller with load observation kept the locomotive speed stable when the working conditions were complex, and the dynamic and static performances of the locomotive and the antijamming performance were improved.