Abstract: X-ray radiographic inspection on the butt joint of 10CrNi3MoV/BFe30-1-1 clad plate elbow manifestes that there are two obvious strips of linear traces on the weld and the defect is hard to be determined by weld defect assessing methods and experience. The defect is analyzed in this paper and it is suggested a continuous hole between the transition layer weld and the clad. An improved the groove type and the welding procedure are proposed to avoid this kind of defect.