Convex hull is a very important data structure of computational geometry design. This paper presents an algorithm to construct the convex hull of a set of scattered points by coordinates and relative angle method. The algorithm determines the convex vertexes and eliminates some non-convex vertexes, which greatly reduces the searching scope and the complexity. Delaunay triangulation is widely used in 3D surface reconstruction. Due to its duality, Delaunay triangulation is usually constructed through Voronoi diagram. Delaunay triangulation is directly constructed in this paper. The algorithm is simple, stable and easy to implement, especially for less data points.