The invention relates to the technical field of oil exploitation, in particular to a wedge mechanism of a cold pipe bender. The wedge mechanism of the cold pipe bender comprises a first main push oil cylinder, a second main push oil cylinder, a movement block, a fixing block and a lower tire sliding block, wherein the first main push oil cylinder is fixed to a bottom plate of the cold pipe bender; one end of the first main push oil cylinder is connected with the movement block; the second main push oil cylinder is fixed to the bottom plate of the cold pipe bender; one end of the second main push oil cylinder is connected with the movement block; the fixing block is fixed to the bottom plate below the movement block, and is provided with a first slope surface; the first slope surface faces towards the movement block; first rolling components are arranged on the first slope surface; the lower tire sliding block is positioned on the movement block; second rolling components are arranged on a first surface, facing towards the movement block, of the lower tire sliding block; and a lower tire connecting part is arranged on a second surface, opposite to the first surface, in the lower tire sliding block. With the adoption of the wedge mechanism of the cold pipe bender, the problem that with the increasing of the pipe diameter of a bent pipe, the size and weight of the cold pipe bender are increased significantly in the prior art is solved, and the bending ability of the cold pipe bender is improved.