Abstract: Addressing the actual operation circumstances,the co-authors make an analysis concerning the different straight welding processes （UOE,JCOE and HFW）vs stress-strain relationship during the pipe-making process. And the law of tensile strength variation as takes place in the pipe-welding operation is studied by means of the deformation reinforcement and Bauschinger effect theories. The conclusion of the study can be used as the theoretical basis for preparing technical terms for purchase of steel plates（strips）,optimizing pipe manufacturing process parameters and adjusting tensile strength of finished products.