In surface machining, the tool path is one of the key factors affecting the machining efficiency and quality, whether the tool path is reasonable is very important. Combining with the process of gas cap, the tool path generated by PowerMILL software was studied. It was found that in the processing process, too much lifting cutter, pointed tool path existing in steep part, uneven tool path distribution seriously affected the parts machining efficiency and surface quality. To solve this problem, optimization scheme of tool path was put forward, products processing efficiency and surface quality were improved. It has certain reference significance to actual production.