The sea-sky background image has a large area of sky and the target must be near the sea-sky-line when looking from a distance. The existing dehazing algorithms improve the sky area by weakening the processing of the sky area. This will inevitably weaken the dehazing effect near the sea-sky-line and be detrimental to the next target detection. This study proposes the method of atmospheric scattering physical model to dehaze. Firstly, based on the features of the sea-sky background image, the edge detection algorithm is used to divide the image into sky and non-sky regions. Considering the physical meaning of atmospheric light, the maximum value of the sky region is estimated as the value of atmospheric light. Secondly, the cost function is designed based on the prior information that the fog image has low contrast and the fog-free image has high contrast, and dividing the image into blocks by SLIC superpixel segmentation. The rough transmission is estimated by finding the minimum of the function in each block, and then the guided filtering is used to eliminate block effect. Finally, the fog-free image can be obtained by substituting the parameters obtained in the first two steps into atmospheric scattering model. The experimental and analysis results show that this method can achieve better dehazing effect of sea-sky background images.