To solve the problem that beam drift errors have a significant impact on the performance of ultra-precision laser collimation measurement systems and th ey are difficult to be extracted,a real-time compensation method is presented base d on average filter.In this method,the influence of interference noise is suppresse d with a moving average filter, and useful beam drift signal and its trend,as compens ation variation,are effectively extracted from actual weak detection si gnals.In this way, beam drift is then real-time feedback compensated by using of a Piezoelectric t ilting mirror system,in order to suppress its impact on the stabil ity of laser collimation system.Experiment results indicates that:when the output beam is tested in this method with distance of 1m over 140second,the standard deviation of beam drift in Xdirection is decreased from 2.66×10－8 rad to 4.13×10－9 rad,and in Y direct ion from 1.74×10－8 rad down to 3.97×10－9 rad.In another word,t he directional measurement stability is effectively improved for the laser colli mation measurement system.