Abstract: In order to cut the holes and beveling the grooves for nozzle and tubular connection welds on the wall of pressure vessels,an automatic contour-saddle cutting machine has been developed.The results,from the applications in last three years,have shown that the accurate shape and dimensfon,the smooth quality of surface have been obtained with this kind of cutting machine.The paper presents the design of tracking mechanism,discusses the tracking accuracy for the cutter along the curve of saddle and the deviation of hole size etc.The approval test of cutting process is introduced.