The utility model relates to a bending tool for a cage ladder retainer. The bending tool comprises a rack, a fixed wheel, a rolling wheel, a connecting frame, a push rod and a limit device, wherein the connecting frame consists of an upper connecting plate and a lower connecting plate that are integrated into one; a vertical shaft is fixedly connected on the rack; the fixed wheel is arranged between the upper and the lower connecting plates and is pivoted with the upper and the lower connecting plates by the vertical shaft; the rolling wheel is arranged between the upper and the lower connecting plates and is connected with the upper and the lower connecting plates by a pin shaft; the fixed wheel and the rolling wheel are in the opposite-rolling installation; wheel grooves are arranged on the outer circumferences of the fixed wheel and the rolling wheel; one end of the push rod is connected with the end part of the connecting frame; the limit device consists of a first limit block and a second limit block; the first limit block is fixed on the rack and is used for limiting the end part of retainer material; and the second limit block is used for limiting the push rod to drive the connecting frame to rotate around the vertical shaft to the required angular position. With the application of the bending tool, the cage ladder retainer of a derrick is formed at one time by the cold-bending manufacturing and does not need welding, thereby greatly improving the working efficiency and lowering the production cost; compared with the traditional process, the appearance quality of the retainer after the cold bending can be improved greatly.