Abstract: Micro-motion feature is an important basis for mid-course warhead discrimination. The target aspect angle is changing approximately periodically during the micro-motion period. Thus the high-resolution range profile (HRRP) sequence is changing the same way. Based on the analysis, a new method is proposed to extract the micro-motion period by estimating the period of HRRP sequence's maximum sliding correlation coefficient. Simulation results show the effectiveness of the proposed method.