As for the sensorless control of interior permanent magnet synchronous motor (IPMSM), conventional high frequency (HF) pulsating signal injection method is widely used, which uses band-pass filter (BPF) and low-pass-filter (LPF) based phase-locked-loop (PLL), however it may face the problems of poor stability and long convergence time. Therefore, an improved signal demodulation algorithm based on moving-average-filter (MAF)-PLL is proposed. MAF, which makes full use of the HF signal periodicity and half-wave symmetry, has higher bandwidth and better harmonics suppression ability than BPF or LPF. Furthermore, a proportional-integral (PI) regulator is used to gain the rotor speed and an integrator is applied to estimate rotor position. Compared with the conventional method, the proposed method gets rid of BPF and LPF, contributing to improving the stability and dynamic performance. Besides, undetermined parameters are reduced to one, i.e., window length of MAF, avoiding complex parameters design and selection. The proposed HF pulsating injection method has simpler signal demodulation process and is easy to implement. Finally, the experimental results have verified the feasibility and effectiveness of proposed method.