Given the problems of excessive enhancement and information loss caused by space change in the processing of color image enhancement, we propose a method to enhance color images in RGB space based on mathematical morphology top-hat algorithm, which utilizes standard deviation weight ratio of each component as the regulatory factor. Firstly, we extract the bright and dark features under multi-scale of R、G、B channels. Secondly, we use control factors to enhance valuable detail features. Finally, we combine the three components to get the enhanced target image. Experimental results indicate that the method can effectively enhance image contrast, avoid excessive enhancement, keep the brightness, and has good visual effect.