The utility model relates to an unmanned aerial vehicle undercarriage connecting device, upper plate and hypoplastron including undercarriage, mounting disc, being equipped with mounting hole no. 1 on the upper plate, being equipped with mounting hole no. 2 on the hypoplastron, the undercarriage includes supporting legs, bracing piece, sleeve pipe no. 1, sleeve pipe no. 2, screw rod, and wherein, the bracing piece tip is equipped with L type groove, and the supporting legs is connected with the bracing piece is perpendicular, and mounting hole no. 1, mounting hole are arranged in between two to sleeve pipe no. 2, and the internal diameter of sleeve pipe no. 2 is greater than the aperture of mounting hole no. 1, mounting hole no. 2, and sleeve pipe no. 1 passes mounting hole no. 1, sleeve pipe no. 2, mounting hole no. 2, bolt traversing sleeve pipe no. 1, sleeve pipe no. 2, two together fixed with sleeve pipe no. 1, sleeve pipe, bracing piece tip inserted casing one, L type groove through the bracing piece tip with the bolt is pegged graft and is rotatory, makes bracing piece and mounting disc link together, the terminal surface of sleeve pipe no. 1, sleeve pipe no. 2 is the inclined plane, the bracing piece with the contained angle is the acute angle between the axis. The utility model discloses simple structure, installation easy maintenance, processing is also convenient.