Abstract: Submarine has complex outer and inner structures. For predicting echoes of submarine, the inter-shelters between different plate elements of the submarine must be taken into consideration. In this article, an exact model of Benchmark submarine is established by 3D model-building software, and then two groups of surface meshes of different sizes are built up as the plate elements of the submarine. The fine meshes are taken as the object meshes to be sheltered, and the large ones work as the sheltering meshes in this algorithm, rather than only the fine meshes are used in the existing sheltering algorithm. Due to reducing the number of total plate elements, the computing speed of the improved algorithm is increased. Comparing the results of predicted target strength and computing speed of the improved algorithm with that of the original one, the former has great advantages in computing speed and accuracy, and shows more potential in engineering application.