The invention discloses a morphing mechanism for a vertical takeoff and landing unmanned aerial vehicle. The morphing mechanism is designed at the rear part of a vehicle body of the unmanned aerial vehicle so that the unmanned aerial vehicle can have two flight modes, namely, vertical takeoff and landing and efficient cruising. The morphing mechanism is divided into two constituent mechanisms, one is a morphing driving mechanism used for driving upper and lower parts of a rear aerial vehicle body to synchronously rotate, and the other is a screw propeller orientation constraint mechanism used for guaranteeing that the orientation of a screw propeller at the vertical fin tip part keeps consistent with the axial direction of the aerial vehicle body in the morphing process. The morphing mechanism enables the unmanned aerial vehicle to morph between the vertical takeoff and landing mode and the efficient cruising mode, so that the control difficulty is reduced in the mode morphing process, and the morphing process is stable and safe.