The invention discloses a tilting quad-rotor long-endurance composite aircraft which comprises a quad-rotor system, a tilting mechanism and an aircraft body. The quad-rotor power system is provided with four propellers driven by four propeller engines. The tilting mechanism is installed in the middle of the aircraft body through a tilting shaft and is provided with four engine supporting mechanisms arranged peripherally. The end of each engine supporting mechanism is provided with one propeller engine. When the tilting shaft is perpendicular to the horizontal plane, two propeller engines are arranged in front of wings, two propeller engines are arranged behind the wings, and the propeller engines are located on the left side and the right side of the aircraft body respectively and are symmetric. Meanwhile, the two propeller engines located on the left side and the right side of the aircraft body are symmetric. During vertical takeoff, the quad-rotor power system mainly provides lift force in the vertical direction; after takeoff, whole tilting and locking of quad-rotors are achieved through the tilting mechanism, and the aircraft body gets into a level flight mode. The aircraft has the advantages that safety and reliability are high, the propellers in the quad-rotor power system are not blocked by the wings, efficiency is high, and the efficiency of the wings is improved.