Abstract: Mathematical model of defects depth and deviation for butt joint weldment was established,and the spatial position of defects was determined. Mathematical model of weld profile was provided,and perfect presentation of weld profile was achieved. Defects visualization interface of butt joint weldment was designed,and the butt joint weldment model was established,after the bulk defects of automatic extraction for butt joint weldment were import,the spatial position of bulk defects of butt joint weldment was reappeared. Adjustment of weldment parameters,visualization angle and transparency were introduced,and the three views of visualization model were shown,which could provide better basis for defects repair,welding procedure setting,defects spatial distribution feature research and structure integrity evaluation of butt joint weldment.