The automatic exposure algorithm plays an important role in image acquisition and subsequent processing. A self-adaptive damping smooth automatic exposure algorithm for CMOS cameras is proposed to address the shortcomings of current smooth automatic exposure algorithms on mobile platforms. Calculate the average brightness of the region of interest in the image and compare it with the target brightness to determine whether to perform automatic exposure. Calculate new exposure time and simulation gain based on exposure strategy and exposure status. The new exposure time and analog gain are applied after adaptive damping smoothing to complete automatic exposure. The experimental results show that the proposed algorithm can accurately, quickly, and smoothly achieve automatic exposure control in various lighting environments.