The bending causes of 34CrMo4/1 accumulator pipe in the cold bed after hot rolling are described. Through analyzing chemical composition and microstructure of the steel, pipe bending is due to the stress for microstructure ununiformity. After comparing the CCT curves of bending pipe and nonbending pipe, it was found that the content change of Cr and Mo in the thickwalled steel pipe influences aircooled microstructure. An appropriate reducing or increasing Cr or Mo elements, the CCT curves moved toward left or right can impede or stabilize bainitic transformation to avoid pipe bending for microstructure stress in cooling bed.