The invention provides an atmosphere protection device for wire arc additive manufacturing. The device comprises an upper seat and a lower seat. The lower seat is a hollow shell. The upper end of the shell is connected with the lower end of the upper seat. Multiple through holes which are distributed uniformly are formed in the lower end face of the upper seat, so that an air sifter is formed. The center of the upper end face and the center of the lower end face of the upper seat are each provided with a through hole matched with a welding gun. The welding gun sequentially penetrates the through hole in the upper end face and the through hole in the lower end face of the upper seat and is inserted into a cavity of the lower seat and then fixedly connected with the upper end of the upper seat. A ventilation hole is formed in the side wall of the upper seat. An external air inlet pipe is inserted into the ventilation hole, and inert gas is introduced into a cavity of the upper seat. The gas flows along the inner wall of the upper seat, enters the cavity of the lower seat through the air sifter and then flows out through a lower end opening of the lower seat, so that atmosphere protection in the welding process is achieved. By means of the atmosphere protection device, the atmosphere protection scope is expanded, and defects caused by overlapping of multiple formation layers are eliminated.