This study proposed an image background blurring algorithm based on color constancy. First, color constancy was used to detect the illumination of the image using which the Lambertian surface model was constructed. Next, the maximum mask pixel difference was compared with the maximum local pixel difference, and the image depth map was obtained using the soft matting algorithm. Furthermore, the image was divided by the gray value to obtain the foreground and background portions. Finally, the image background was blurred using the Gaussian filter. Using the proposed method, the foreground and background of the monocular image can be accurately obtained and the blurring effect is obvious.