Abstract: Under the different color temperature of light sources, the colors of images obtained by CMOS image sensors will be different, it was likely to happen that it deviate from the real color, resulting in a decline of image quality, seriously affecting the effective of high -definition electronic endoscope. Proposes an auto white-balance algorithm based on achromatic surface detection, using the sum of RGB three -channel of each pixel to detect the achromatic surface. With the achromatic pixels set, the illumination chromaticity was estimated, and then correct the colors of image, through the diagonal transformation of endoscope image in real -time auto white -balance algorithm, modified the color deviation phenomenon. This real time, effectively algorithm eliminates the color deviation phenomenon caused by different illuminate condition, which is in accord with the color with the color characteristic of human visual system.