Abstract: 308L stainless steel straight wall pieces were fabricated by TIG arc additive manufacturing. The microstructure and mechanical properties were studied. The solidification mode of austenitic stainless steel was used to predict the microstructure, and the microstructure of the forming part was analyzed by SEM and EDS. The results show that the predicted microstructure is consistent with the actual microstructure, which is austenite and a small amount of ferrite. The microhardness of the bottom and top of the additive part is higher than that of the middle structure, that of the bottom is the highest, and that of the top is the second. The specimens were sampled from the part in horizontal direction for tensile test, and the fracture mode is ductile fracture. The minimum tensile strength of the forming part is 520.19 MPa, the minimum elongation is 41.7%.