Abstract: The part fabricated by welding rapid prototyping has excellent mechanics capability, so welding prototyping will be widely applied in the future. But welding is a processing of local high temperature, the distribution of temperature field will affect the quality and performance of welding part. In this paper, one-layer depositing of thin-wall part was studied. Numerical simulation was done by ANSYS, and the influences of scan path on temperature field and stress field were analyzed. This study will offer theoretical foundation to accurataly choose the scan path in the welding rapid prototyping.