3D flexible cold roll-forming production line is designed and manufactured specifically for roll forming of truck U beams and reinforcing beams with constant section. It can uncoil, level and roll form the metal coils into U beams and reinforcing beams, and the formed beams are cut off by the production line with the required length. According to the wide varieties of characteristics of U beams and reinforcing beams,the production line can automatically adjust the center distance and axial gap of the upper and lower forming rolls to meet the need for changes in the material thickness, web width, and flange height of U beams. Therefore, in this case, the truck beam specifications can be quickly converted without changing the roll, greatly improving the production efficiency.