A system for dynamic range expansion of digital images includes: an optimizing device configured to calculate and store the output histogram of the previous frame of image data, calculate and obtain the mapping function according to the output histogram of the previous frame of image data and obtain the mapping table of the previous frame of image data according to the mapping function; and a mapping device configured to receive a next frame of image data and process the next frame of image data with the mapping table of the previous frame of image data to generate the enhanced image data. The present system enables processing ultrahigh definition images with very low requirements on hardware requirement. There is further provided a method and a non-volatile storage medium for dynamic range expansion of digital images.