This paper presents a study of the transient performance of the speed and position sensorless control of an interior permanent magnet synchronous motor (IPMSM) based on back-electromotive force (back-EMF) estimation method in the rotor reference frame. The fundamental characteristics of the estimated back-EMF, position and speed components using mathematical models of the IPMSM are analyzed. The analyzed sensorless control has back-EMF estimator, rotor position estimator such as a phase-lock-loop (PLL) type estimator, and disturbance observer. To improve the transient stability, the selection methods of major factors such as for sensorless control algorithm and the angle compensation method using a current feedback control are introduced. The dynamic performance of the proposed strategy in transient state is verified through simulation and experimental results.