At present, most digital cameras take color images with red, green and blue components using 8-bit color depth bits. When these images are processed, analyzed and processed to extract information from the image or to satisfy the visual and psychological requirements, the processed images are prone to color slicing, especially when the image is enlarged,which is not conducive to the subjective visual effect of the human eyes.The larger the color depth, the more detailed the color change. Images with more than 8 bits of color depth have better performance in later processing. This paper expands the color depth of the image by averaging multiple images, and enhances the low illumination image after color depth expansion. The experimental results show that the color change of the high color depth image after processing is smoother and delicate, and the resulting image quality is higher. The validity of this method is verified and it has some practical value.