As for the drive of control system in electric vehicles, if the inverter power is supplied by a constant DC-link voltage, there are some disadvantages in the system, such as small utilization of the voltage, big current harmonic distortion of the motor windings. A new strategy for vector control of permanent magnet synchronous motor (PMSM) with variable DC-link voltage is proposed, which is suitable for electric vehicles. According to the reference voltage amplitude of the inverter, the new system uses bidirectional DC/DC converter to adjust the DC-link voltage to improve the performance of the vector control system. At last, the whole system is simulated with MATLAB software. The simulation results show that the new strategy for vector control can increase voltage utilization, decrease torque ripple, improve current waveform effectively and decrease the total harmonic distortion of motor current. The results also verify the effectiveness and feasibility of the new strategy.