A novel adaptive dimming method for clear ground scanning imaging of airborne electro-optical (EO) system was proposed, which could solve the problem that the image quality of the EO system deteriorated when the scanning scenes changed rapidly. Based on the traditional automatic detection and dimming technology, the three-level adjustment strategy was adopted to reduce the contrast difference between frames and lines of image brightness of reconnaissance videos by the adaptive dimming method of on-board imaging sensor and the contrast correction algorithm of the video processing board. After being processed by ground intelligence processing unit, a continuous image sequence of ground scanning with uniform and consistent image contrast was obtained. The test results show that after processing scene images with large differences by this method, the image contrast, average gradient and information entropy increases, which effectively improves image quality and overall image contrast and clarity, and lays a foundation for subsequent intelligence information processing such as target detection, tracking and stitching based on image sequences.