Aimed at the problem that the gridaided algorithm does not perform well in constructing convex hull of a ring-distributed point set, a gridreprocessing algorithm was proposed. By comparing the spatial relationship between related cells, the proposed algorithm eliminated most of the points never proved to be vertices of the convex hull twice. As a result, the number of points to be Grahamscanned was greatly reduced and the computational efficiency improved. The experimental results show that the grid-reprocessing algorithm significantly improves the efficiency of handling ring-distributed point sets and is more efficient, to a certain extent, than the grid-aided algorithm when dealing with evenly distributed point sets.