Due to the absorption and scattering of underwater light, the underwater images often have color distortion, low contrast and fuzzy details.Therefore, a weighted fusion based multi-space transformation method is proposed for underwater image enhancement.Firstly, white balance processing is made to the image, which can effectively correct the blue (green) color appearance of the image.Secondly, the RGB space is converted into LAB space by the white balanced images, and the L channel is processed with the improved adaptive Gamma correction, and converted back to RGB space.Then, CLAHE and bilateral filtering are carried out in RGB space.After that, the RGB space is converted to HSV space, and the single scale Retinex algorithm combined with guided filtering is used to process the V channel, and then converted back to RGB space.Finally, weighted fusion and detail enhancement are carried out to the above three results, and the final enhanced image is obtained.Experimental results show that the proposed algorithm is effective for improving the contrast and sharpness of underwater images and removing color distortion.