The welding craft equipment structure of the existing wainscot flange is simple and has small pressing force using the welding method of manual welding, while great residual stress and deformation can be obtained in the seam after welding, resulting in bad stability of welding quality. Therefor it can not meet the demand of the products. This paper starts from the influence factors upon flange welding quality, a flange automatic welding craft equipment was developed. Basing on the simulation methord the optimal interference fit quantity of 0.15 to 0.25mm between flange and the aperture has been obtained. The methord of installing wainscot firstly and then flange can effectively prevent the assembly cracks. Heating the bearing plate before welding solves the problem of priming cracks. The appearance of the flangewhich welded by automatic welding process is beautiful, while welding defects are reduced by more than 70% compared with manual welding. The average tensile strength of welded joints at low temperature (-196℃) reached 348MPa, and the elongation reached 6.7%.