In the control procedure of process based on machine vision, the key is the location of the special point on work piece. The difficulty lies in how to construct a shape descriptor that can meet the needs of shape matching, precision of location and real-time at the same time. To solve the problems above，a kind of shape matching and localization algorithm based on polygon fitting is proposed. The method is aimed at the planar two-dimension (2D) contour. The key points on the contour are gained by the polygon fitting processing, then the polygon is used to construct a shape description and the key points are used to make location, to obtain the transformation relationship between template contour and target contour. The results show that by using the proposed rotation invariant shape descriptor, high accuracy and good real-time performance of shape matching and location algorithm can be gained.