Focused on the problem that the control accuracy of the d-axis currents and quadrature axis will descend with the varying of the motor speed, a new kind of linearization compensating method of current vector decoupling control is proposed. Based on the idealized dealing with permanent magnet synchronous motor (PMSM), the mathematical models and control models are established, and the program flow chart of current vector control method is designed. Then a speed control system of PMSM is established in the test environment, two phase motor currents and the DC voltage are measured separately by current sensors and voltage sensor. The experiment result proves that after compensating with the growth of the motor speed, the accuracy of id is increased obviously so that the decoupling control performance of motor currents is improved effectively.