3-dimensional scanner is a data acquisition tool in recent years. The scanned datum are 3-dimension discrete points. Veracity of approximation curvature of 3-dimension discrete points is difficulty. In this paper, according to geometrical properties of 3-dimension curve, a method of curvature calculation of 3-dimension discrete points on edge curve is introduced. Concretely, Firstly, feasibility in theory of method in this paper is proved; secondly, virtual arc is used to approximate discrete edge curve, so that curvature and correction-curvature will be calculated; thirdly, method in this paper is contrasted with method dealing with similar question in experiment, and the result of experiment manifests that accuracy of method in this paper is better than method contrasted; finally, an application experiment is made.