Abstract: The variable leakage flux permanent magnet synchronous motor(VLF-PMSM) possesses the advantages of wide speed regulation capability and high efficiency under extensive range, which meets the requirements of the motor drive system for electric vehicle applications. However, its special characteristics of parameter variation at different operating conditions will bring about great challenges to its sensorless control research. To overcome this problem, a sensorless control method at low speed based on parameter-sensitive adaption was proposed in this paper. Firstly, the mechanism of inductance variation and the relationship between saliency ratio and position estimation error was analyzed, then the influence of the saliency ratio variation on the system stability was analyzed. Thence, the parameter adaptive detection filter and sliding mode controller were designed. The center frequency of the detection filter was adaptively adjusted through the speed. Also, the dynamic adjustment factor was introduced to improve the rotor position estimation accuracy. And the dynamic and steady-state response of the VLF-PMSM sensorless control drive system was greatly improved. Hence, the influence of the changed motor parameter on the sensorless control system was suppressed. Finally, the VLF-PMSM sensorless vector control system was established, and its experiment was conducted. The experimental results verify the feasibility and effectiveness of the proposed control strategy.