A fast efficient method for extracting body boundary from helical surface is proposed in this paper in order to build the model of the measured surface. Firstly, according to the density of the point cloud, a divisional cylinder is built from an established model of the helical surface. Secondly, a center of the circle is get from the XY projection of the point cloud by the least-square method, and the points are sorted to make the point cloud in sequence. Then a vector method is used to test the remaining point cloud, which is separated by the divisional cylinder to obtain the rough body boundary points. The rough boundary is modified by the angles between the points to obtain the accurate body boundary points. Finally, a smooth boundary is formed through the B-spline method. The expereimental results show that the proposed method does not need grid partition and boundary grid detection and the efficiency is very high.