The invention discloses a special assembling trolley for wheel sets of cranes, which comprises an assembly stand. A clamping mechanism used for clamping a wheel set is arranged on the upper surface of the assembly stand and consists of a movable clamping block, a fixed clamping block and a driving device, the fixed clamping block is fixedly disposed on the upper surface of the assembly stand, the driving device which is used for driving the movable clamping block to move in directions far away from and close to the fixed clamping block is arranged on the assembly stand, a trolley support frame is fixedly connected to the lower surface of the assembly stand, universal wheels are fixedly connected to the bottom of the support frame, and one end of each universal wheel is provided with a brake device for braking the trolley. The clamping mechanism on the assembly stand is favorable for vertically assembling the wheel set, various assembly dimensions can be adjusted conveniently and can be well guaranteed, simultaneously, safety is ensured, two sides of a bearing box of the wheel set can be assembled simultaneously, assembly working hours can be greatly reduced, and the trolley can be braked at an optional position by the aid of the braking devices, and is fine in safety performance.