Abstract: 316L austenitic stainless steel thin-walled samples were formed by cold metal transfer (CMT) based on wire arc additive manufacturing (WAAM) method. The forming width, side forming error, deposition efficiency and microstructure of the samples under different welding parameters were investigated. The results show that when the parameters are consistent, the width of the formed specimen increases with the decreasing of the welding speed. The side forming error reduces firstly and then increases with the increasing of the heat input. The deposition efficiency increases firstly and then reduces, and the side forming error and the deposition efficiency trend are the opposite. The more the deposition efficiency, the lower the side forming error, and the forming efficiency can reach more than 90%. The microstructure of the formed parts consists of γ-Fe phase and δ ferrite phase. The microhardness tests show that the hardness along the vertical and the deposition direction did not change significantly, which is related to the uniform microstructure of the sample.