In permanent magnet synchronous motor system, the use of high resolution mechanical position sensors may increase the system volume and cost and reduce the system reliability. Presents a sensorless control algorithm for the interior permanent magnet synchronous motor (IPMSM) based on the Luenberger observer with low resolution Hall startup, and applies the algorithm to estimate the rotor angle and speed. The simulation results show that:1）The transition process from the Hall sensor algorithm to the sensorless control algorithm is smooth, the current waveform possess a continuous sine characteristic, less harmonics and less noise; 2）The control system is efficient, and the working efficiency is higher than 80% within the speed range of 1 000~4 000 r·min-1; 3）The cost of the control is lowe.