Aiming at the problems of color distortion and visual blur in underwater images, an underwater image restoration algorithm based on light attenuation prior and background light fusion is proposed. First, the background light 1 is calculated by the maximum intensity a priori, and the background light 2 is estimated by the image quadtree method. The two local background lights are fused according to the brightness and darkness of the underwater image illumination to determine the global background light. Secondly, the relative depth of the scene is estimated a priori according to the light attenuation, and then the transmittance of the three channels is calculated. Then the underwater optical imaging model is solved inverse to eliminate backscattering. Finally, the adaptive histogram equalization algorithm with limited contrast is combined to better correct the color distortion of the underwater image, and finally the restored underwater image is obtained. Conduct subjective and objective evaluation comparison experiments with four representative underwater image restoration methods. The experimental results show that the proposed algorithm can effectively remove the visual blur of underwater images, and the visual effect is closer to the images in natural scenes.