The invention discloses a highway greenbelt tree pruning device, which is provided with a cutting part, a walking part, a servo cylinder and a connection plate, wherein the walking part comprises a walking wheel assembly and a supporting frame arranged on the walking wheel assembly via an elastic damping mechanism; the lower part of the supporting frame is provided with the connection plate; the walking part is connected with the side wall plate of a traction vehicle via the connection plate; the servo cylinder is hinged and assembled at the upper end of the supporting frame; the cutting part is a horizontal chain cutting mechanism; the left end and the right end of the chain cutting mechanism are both provided with fixing frames; the left fixing frame and the right fixing frame are connected via a horizontal supporting plate; the right fixing frame and the supporting frame of the walking part are hinged and assembled; and the left end of the horizontal supporting plate is hinged and assembled with the telescopic arm of the servo cylinder. The highway greenbelt tree pruning quality and person safety of workers can be ensured, and normal operation of the highway is not seriously influenced.