Abstract: The traditional contour offset path planning strategy for arc-based directed energy deposition of medium-sized complex parts has a high degree of geometric fidelity. However, continuous offsetting of original contour can easily lead to underfilled regions and defects, that can be forming the area to be optimized. To address this, a precise defect identification method based on Boolean operations is proposed. The defect region is obtained by calculating the Boolean difference between the original and backtracked polygons. This region is reconstructed into skeleton-filled areas through filtering and merging. The optimal filling direction of skeleton-filled areas is determined by the minimum rectangular box, and the zigzag path is generated. Finally, the contour offset path is reclassified and connected to form a continuous forming path. The forming path of skeleton-filled areas is firstly transformed into machine code. In the subsequent forming test, the propeller parts were printed by the robot arc additive manufacturing system. The results indicate that the parts have achieved the expected forming size, and there are no defects in the traditional method. This proves that the method has highly feasible and applicable.