Abstract: Studied here in the paper are such aspects as pipe-shaping control during the pipe-forming process,expanding parameter control,and welding strain,etc.Also analyzed are the influences on the straightness of the SAWL pipe,including the asymmetric welding deformation,the differences of the longitudinal shrinkage ratio and deformation between the weld seam and the base metal,and the weld seam "pout" defect,etc.and the regularity of straightness change caused by welding strain process of steel pipe is simulated by the ABAQUS software.The results show that the straightness can be obtained within 0.15%L by means of adopting pre-strain, "pout" control and reasonable expanding strain rate,so as to avoid the problems such as pipe groove processing,pipe end oblique cutting,and uneven 3PE coating or insufficient thickness.