Aiming at the problems of fogging and color distortion in underwater images caused by the absorption and scattering of light by water, an underwater image sharpening based on fusion of restored structure and enhanced texture is proposed. Firstly, the image is decomposed into a structure layer and a texture layer by the relative total variation model. Secondly, the background light value is calculated based on the high brightness, flat characteristics and color information of the background light, the transmittance is optimized by using the red dark channel prior. The restored structure layer is obtained by inversely solving the imaging model. Then, a gradient smoothing method is proposed for the texture layer, which can effectively enhance the texture details while suppressing the noise. Finally, the restored structure layer and the enhanced texture layer are fused to obtain a clear underwater image. The experimental results show that the proposed algorithm combines the restoration and enhancement technology, the sharpened image can better remove the fogging phenomenon, and the color is bright and the details are rich. Compared with the comparison algorithms, the underwater color image quality evaluation index is improved by 16.09%, which provides a feasible reference for engineering practices such as underwater robots.