In aerospace and deepwater servo applications, current and position sensors will increase the size of the driver. Sensor failure will seriously affect the control effect of the system, and reduce the reliability of the system. To address this issue, some scholars have proposed a sensorless control scheme based on phase current reconstruction. However, these methods always concentrate on issues when the motor operates under medium speed without considering the startup problem. For that, an adjusted I-F startup strategy that is suitable for current reconstruction is proposed in this paper and a non-linear current regulator is proposed to make the motor switch smoothly from single-loop to double-loop control. Finally, the feasibility of the whole scheme is verified through experiments, and the reconstructed current, location estimation and switching effect are analyzed.