The direct torque control system with hysteresis comparison control method for current AC drive locomotives asynchronous traction motor has shortcomings such as large output torque ripple and high current harmonic content, a direct torque control method of induction motor based on sliding mode control was proposed. A sliding mode flux and torque controller was designed by introducing the exponential reaching law sliding mode algorithm, and its stability was verified by Lyapunov function, an improved direct torque control structure of asynchronous motor was constructed by combining space vector pulse width modulation（SVPWM）. Finally, Matlab/Simulink was used for simulation and comparative analysis, and the conclusion was drawn: compared with hysteresis comparison control method, direct torque control system under sliding mode control method effectively suppressed the output torque ripple of asynchronous motor, and better improved the current harmonics.