To measure the sub-pixel image motion which were caused by satellite attitude instability or vibration,the joint optical transform correlator （JTC) was used,which was based on using the auxiliary plane CCD to record of the image motion in the focal plane of the satellite camera.The principle of this method was described,and the experimental platform was built.Based on which,the measurement performance of the JTC was researched.The results show that,the JTC can measure the sub-pixel image motion of the space camera entirely,and the measurement error submits the normal distribution,which mean is zero and the RMS is no more than 0.12 pixel under the conspicuous level is equal to 0.05,this can meet the operating requirement of the space camera completely.