In order to implement the speed regulation in a wide constant power range for induction motor of electric vehicle, a wide speed field weakening control scheme based on maximum torque control is proposed. The proposed scheme allows the motor to exploit the maximum torque capability in the wide speed range with the constraints of voltage and current of the motor, and then the distribution strategy of excitation current and torque current in the field weakening region is presented. The proposed method reduces the dependence on the motor parameters and has stronger robustness. Simulations and experimental tests were presented to verify the validity of the analysis, which can obtain a satisfactory load capacity in the high speed field weakening region and also can operate at a wide range of constant power region.