In view of problem of large torque ripple existed in low speed range of direct torque control system of mine hoist, an optimal control method of torque ripple for mine hoist was proposed. Based on prediction model, the method uses zero voltage vector injection method to adjust duty ratio of optimal voltage vector. The minimum torque ripple is taken as design index in calculation process of the duty ratio, the optimal duty ratio is obtained by online calculation. The experimental result shows that the method can effectively reduce torque ripple and obtain excellent torque control performance of motor in low speed.