In order to realize the autoexposure of the camera, autoexposure system based on image processing is established. Method of image processing is used to extract the edge of image. By changing the exposure time and gain of CCD, the climbing algorithm is used to find the exposure time and gain of CCD when the edge information reaches the max value. Then, this max value is set to be the final result of one autoexposure process. Experiment result show that the autoexposure process is finished within 1 s, and achieve ideal effect. The system has short processing time, wide applied range and accuracy operation. It can meet the requirement of the autoexposure in optoelectronic devices.