The invention relates to a welding protecting device for a stainless steel work piece. The welding protecting device is characterized by comprising a pedestal; the pedestal comprises a first supporting surface and a second supporting surface, wherein the first supporting surface is used for positioning a first work piece; the second supporting surface is used for positioning a second work piece; the pedestal is internally provided with an air chamber and an air hole which communicates with the air chamber; the outer end opening of the air hole is positioned between the first supporting surfaceand the second supporting surface and is exposed outside; the wall of the pedestal is also provided with an air charging hole and a cooling water passage, wherein the air charging hole communicates with the air chamber; the cooling water passage is connected with the external environment; a supporting plate is also arranged inside the air chamber; the upper end edge of the supporting plate is accommodated between the first supporting surface and the second supporting surface; a clearance is formed between the two side surfaces of the supporting plate; another clearance is formed between the two sidewalls of the air hole; and the clearances both communicate with the air charging hole through the air chamber. The welding protecting device provided by the invention realizes rapid heat radiation, prevents deformation and color changes of a part, prevents dropping of molten metal liquid, commendably controls the shape of a weld pool and guarantees the welding quality.