The optical joint transform correlator (JTC) is an effective technical way for image motion measurement of the space camera. Its basic principles are presented，and performance is evaluated through static simulation experiment. A calibrated image set is tested by the experimental device. The results show that, the measurement accuracy can be controlled below 0.2 pixel in two directions, which is satisfied for the space camera. The influence of centroiding window size on cross-correlation peaks locating is analyzed, based on which, intensity weighted centroiding (IWC) is proposed instead of the traditional centroiding method, by which not only the influence of centroiding window size on image motion measurement is reduced, but also the measurement accuracy is improved.