Abstract: Amplitude data are the key data for generating backscatter intensity maps as well as seabed sediment classification. There are noises in signals because of the system itself or some other factors when the amplitude data are obtained. The existence of these noises directly effects data processing, which makes seabed backscatter strength map distorted. So the amplitude de-noising becomes very important. Spatial filtering methods in the image processing are referred to. By comparison and analysis with the actual observations, we prove that the gradient inverse weight smoothing algorithm is optimal, and the experimental results show the correctness of the conclusions.