Phase current detection is the key factor of the Induction Motor Direct Torque Control System, the paper designs a more simple, practical and high accuracy phase current detection circuit using in asynchronous motor direct torque control system. Using new current sensor chip ACS712, the invert bridge arm sampling mode, accurate detection of current. Error calculation, using MATLAB fitting and giving the experiment results. With TMS320F2812 as the master controller to verify the correctness of the detection method. The results show that the circuit has high detection accuracy and linearity and can be widely applied in AC speed regulation.