Due to the asymmetry of rotor magnetic circuit, the maximum torque per ampere (MTPA) control of interior permanent magnet synchronous motor (IPMSM) makes full use of its characteristic to improve the load capacity. In the actual control, the electrical parameters of IPMSM fluctuate due to magnetic saturation and temperature change, resulting in the actual MTPA control deviating from the predetermined track, so the accurate control cannot be realized. In view of the change of parameters, MTPA control in the electric vehicles mostly adopts the look-up table method, but the process of making the table is complex and time-consuming. In order to solve these problems, the forgetting factor recursive least square method is used to identify the motor parameters online, and the real-time parameters obtained are employed in MTPA control, which improves the robustness and accuracy. The given value of d- and q-axes current is obtained by using the relationship between stator current and d- and q-axes current under MTPA control, which is simple in principle and easy to realize. The model of control system is built by Matlab/Simulink, and the simulation results verify the accuracy and effectiveness of the proposed method.