The invention is applicable to the technical field of unmanned helicopters, and provides a variable-pitch control mechanism of an unmanned helicopter. The variable-pitch control mechanism comprises abody assembly and a rotating assembly used for rotating on the body assembly, the body assembly comprises a steering engine mounting base, a gear box and an anti-torsion ring, and the anti-torsion ring is perpendicular to the steering engine mounting base. A plurality of mounting holes are formed in the outer side wall of the steering engine mounting base, and damping sleeves are arranged on the inner side walls of the mounting holes. By arranging the mounting holes and the damping sleeves, the steering engine and the steering engine mounting seat are fixedly connected through the mounting holes and bolts, and with the arrangement of the shock absorption sleeves mounted in the mounting holes connecting the steering engine and the steering engine mounting seat, the impact brought by alternating loads generated during the vertical movement of the steering engine can be effectively reduced, so that the service life of the steering engine is prolonged.