In the use of real-time auto-focusing technology based on image processing of long range and high resolution aerial camera, the precision decreases due to the influence of image motion. Currently there is no universal theory and exact conclusion on the relationship between image motion and auto-focusing precision. The models of linear motion and jitter are analyzed theoretically, and the mathematical formulas illustrated the influence of image motion on auto-focusing measures are given. The image motion has a negative correlation to maximum value of focusing curve, the larger amounts of image motion, the smaller maximum value of the auto-focus measures. The best focusing position is located at the top of the fitting curve, by making use of the quadratic fitting technology to get auto-focusing curve. The motion base platform for auto-focusing is designed and set up. Experimental results show that when the image motion increases from 1 pixel to 5 pixel, the maximum value of curve decreases from 95.95% to 87.64% . At the same time, the best auto-focusing position on fitting curve is in the high resolution aerial camera’s half depth of focus. This result proves the correctness of image motion theoretical analysis.