Abstract: In order to improve forming efficiency of wire and arc additive manufacturing, advantages and disadvantages of current path planning algorithm were analyzed, and an optimization method of composite path planning based on depth first search (DFS) and ant colony algorithm was proposed. Based on a composite path planning algorithm combining zigzag scanning and contour offset, several zigzag path algorithms with different scanning inclination were used to fill the cross-section contours of porous holes, and zigzag scanning path partitions were connected by depth-first search algorithm to reduce number of path bars, arc-starting and arc-extinguishing times of zigzag scanning path. Then, ant colony algorithm was used to search filling sequence of path and optimum combination of arc-starting and arc-extinguishing points, so that the total free travel length of filling path was minimized. The simulation results showed that DFS partition connection algorithm played a good role in zigzag path planning for different scan inclination. The planning optimization method of wire and arc additive manufacturing path based on ant colony algorithm could effectively reduce empty travel length.