The machine adopts a 3-roller symmetrical structure. the upper roller makes vertical movement at a symmetrical position in the center between the two lower rollers. the hydraulic driving is achieved through the action of the oil in the hydraulic cylinder on the posion. the two lower rollers make rotation and provide the plates with torque through the engagement between the gear of the moderator and gear of the lower roller.several groups of support rollers are devised on the lower side of the two lower rollers to enhance the rigidity of the lower rollers and enables vertical adjustment.on the upper side of the upper roller. there is a rigid beam. and between the beam and the upper roller, there are several groups of support rollers to enhance the rigidity of the upper roller. the machine is fit for bending the work-piece in arc shape and with excessive width.