To measure the sub-pixel image motion which is caused by satellite attitude instability and vibration, an effective approach to measure image motion is presented based on Hybrid Photoelectirc joint transform correlator. Firstly, captured image sequences are optically calculated by joint transform correlator, then the acquired joint power spectrum is processed by Laplace transform, an improved correlation peak is obtained. Lastly, a modified centroid algorithm is proposed to get more accurate motion measurement. Motion measurement based on optical correlation is discussed, and the optical experimental system is also set up. The experimental results show that the measurement error is as low as 0.03 pixel, the accuracy is improved greatly.