The utility model discloses a composite modular multi-purpose investigation unmanned aerial vehicle. The investigation unmanned aerial vehicle comprises an egg-shaped vehicle body, mechanical arms, mechanical legs, rotor wing modules and camera modules, the mechanical arms are uniformly distributed at the top of the side surface of the fuselage along the circumference, and the top of the fuselageis grabbed and fixed through the mechanical arms; the mechanical legs are evenly distributed at the bottom of the side face of the machine body along the circumference, and switching between a slidingmode and a walking mode is achieved through the mechanical legs. The rotor wing module comprises rotor wing supports evenly distributed in the middle of the side face of the fuselage along the circumference and rotor wings installed at the outer ends of the rotor wing supports. The camera shooting module comprises side cameras evenly distributed in the middle of the side face of the fuselage along the circumference and a bottom camera arranged at the bottom of the fuselage. The unmanned aerial vehicle can be switched among multiple states such as aerial flight, suspension and ground crawling,all-weather complex environment operation is achieved, meanwhile, the crustacean shell can resist extreme environments, and the survival and adaptability of the unmanned aerial vehicle are improved.