Based on the theory of direct torque control, the simulation model of asynchronous motor is designed to solve two problems. The one is that asynchronous motor in high speed, if a single circular flux control method used, its switching losses will be great; the other one is that asynchronous motor in low speed, if a single hexagonal flux control method used, it will make a large harmonic current. So double modes are used in solve problems together in this paper. That is when asynchronous motor runs at low speed circular flux control strategy is adopted, and when it runs at high speed hexagon flux control strategy is adopted. Auto-switch between circular flux control strategy and hexagon flux control strategy is achieved. Simulation results show that not only the harmonic current can be reduced, and the switching losses are reduced effectively by smooth switching the two control strategies.