Abstract: The compression method to process power signal was proposed, based on the requirement of power data storage in grinding database. According to the characteristics of the signal waveform, trend points were extracted and sectional lines between them were fitted. A 5-band stepped filter was designed to solve the problem of filter phase deviation. The low passed cut-off frequency was determined by experimental measurement. The 5 points method was employed to extract peak valley points. Combining with prediction method and high- low threshold judgment method, peaks, valleys and abnormal points were accurately withdrawn. Then the first and last points were modified in the extracted data. The power signal compression system was designed and testing results demonstrated that the system can effectively compress data with higher compression accuracy.