Multi-contour processing empty run optimization was regarded as generalized salesman problem. A novel algorithm based on ant colony system optimization and nearest neighbor rule was proposed. Ant colony algorithm was applied to a selected cutting path arbitrarily, an optimal contour sequence was found, with nearest neighbor rule, nodes on each adjacent contour were obtained to construct a cutting path. A new cutting path was built with ant colony optimization algorithm and nearest neighbor rule based on this constructed path. An optimal cutting path was constructed through several iterations in this way. A multi-contour processing instance was given and the results of it indicated a reasonable cutting path could be gained with this algorithm effectively. With single factor analysis and uniform design, the method of how to select optimization parameters was given. 