A multi-rotor unmanned aerial vehicle comprises a fuselage, co-axial twin main rotors, four auxiliary rotors, a fuel engine, a generator and an electric motor. The fuel engine and main rotor shafts are mounted on the middle position of the upper part of the fuselage. The upper main rotor and the lower main rotor which have opposite rotation directions and are distributed uniformly in an X shape are mounted on the main rotor shafts. Auxiliary rotor arms radially connected with the edge of the fuselage are distributed uniformly in an X shape. Motors are arranged at the tail ends of the auxiliaryrotor arms and each motor is connected with one auxiliary rotor. Every two adjacent auxiliary rotors are opposite in rotation directions. The height of the main rotors is higher than that of the auxiliary rotors. The fuel engine comprises an accelerator. The accelerator is connected with a steering gear. The steering gear is connected with a flight control module. The fuel engine is connected with the generator. The generator is connected with an accumulator. The accumulator is connected with a power supply module. A fuel supply system comprises a fuel tank, a fuel pump and a fuel pipe. The fuel tank in which the fuel pump is arranged is fixed to the interlayer portion in the middle of the fuselage. The fuel pump is connected with the fuel engine through the fuel pipe. The bottom of the fuselage is provided with a mission function area at which a camera, a range finder, hanging parts and foot stands are mounted.