The particularity of the underwater optical environment causes fog, color cast, and low contrast in normally captured underwater images. Existing restoration methods suffer from local misestimation in the depth map and inaccuracy in the transmission map. In order to better improve the quality of underwater images, an improved dark channel underwater image restoration algorithm that can balance attenuation and accurately estimate global ambient light is proposed. Construct a depth map through gradient maps and channel differences to obtain global ambient light; obtain a more accurate transmission map by balancing the attenuated dark channel; correct color casts through a white balance algorithm to further improve image quality. In order to verify the effectiveness of the algorithm, experimental evaluations were conducted on the UIEBD data set and RUIE data set. The UIQM index was 1560 and 1668 respectively, and the UCIQE index was 0470 and 0364 respectively. Experimental results show that the improvements proposed in this article can effectively improve the restoration effect of underwater images.