A non-subsample Contourlet Transformalgorithm for underwater image sharpening was proposed to reduce the degradation of underwater image quality.First, the image is preprocessed, the red channel is compensated, and then the white balance and sharpening are carried out. The white balance and sharpening images are taken as the input for NSCT decomposition. For low frequency components, a fusion method of regional variance and weighted Laplace energy sum is proposed. An improved guided filter is used to process the high frequency components. Finally, inverse NSCT transform and color correction are carried out to obtain clear underwater images. Experimental results show that the algorithm corrects the color distortion, improves the image contrast, highlights the details, and significantly improves the quality of the underwater images.