The maximum point of the motor at given speed was found by a quantitative analysis of both the voltage limit vector circle and the current limit vector circle. The maximum torque point was corrected by compensating stater resistance voltage at the voltage limit vector. Through the direct given crossaxis voltage to take full advantage of this point of electromagnetic torque, the motor load capacity and antijamming capability were improved. The simulation proved that the algorithm had been well designed in terms of validity and feasibility. The model has a good portability by the quantitative analysis of the maximum torque point.