Abstract: A high-accurate extraction algorithm of line features of object contour is proposed in this paper, which combines the method of exact positioning of single point and the algorithm of line segment approximation with minimum-distance error. First object contour can be approximated by linear feature. Then we search the adjacent line segment and compute the intersection point between them. At last, we realized the exact positioning of contour cutpoint and provided exact line segment data for 3D measuring and reconstruction based on contour. In contrast to other approaches, the algorithm proposed in this paper has not need good initial value of contour and can get better extraction result. The accuracy of the algorithm is analyzed on real image data. The algorithm has been applied in 3D inspection of diamond, line feature extraction of nuts and industrial sheetmetal parts. The experiment result demonstrates that the algorithm is feasible, correct, stable and exact and can also be extended to other application areas.