Image Motion Compensation(IMC) has been widely used in aerospace cameras to improve the imaging quality and the resolution of cameras. In this paper, the principle of IMC is analyzed and several kinds of IMC technologies used at home and abroad are introduced, such as optical IMC, mechanical IMC, integrate IMC, digital IMC. Then some common methods including parallel-slit method, scan and correlation method, heterodyne method, optical path difference method, direct calculation method are given to obtain an important parameter, speed-altitude ratio. Finally, this paper discusses the developing trend for digital IMC, presents the digital, real-time and miniaturization of measuring speed-altitude ratio and brings forward a new idea for measuring speed-altitude ratio by combining an array CCD with a high-performance microprocessor.