The invention discloses a worm driving rotating mechanism for a threshing cylinder concave board assembly for a thresher and belongs to the field of agricultural machinery. A worm wheel gear ring is fixedly installed at one end of the threshing cylinder concave board assembly, a plurality of pin shafts are evenly distributed on the worm wheel gear ring in the circumferential direction, and rolling bearings are installed at the ends, located on the same side, of the multiple pin shafts respectively. A rolling support ring base is fixedly and coaxially arranged on one side of the worm wheel gear ring, and positioned together with the worm wheel gear ring in the radial direction, the circumferential direction and the axial direction. The rolling bearings are located in an annular rolling slideway groove of the rolling support ring base. A driving worm is arranged on one side of the worm wheel gear ring and meshed with the worm wheel gear ring. By the adoption of the mechanism, rotation of the threshing cylinder concave board assembly is achieved. The mechanism is novel, simple and reasonable in structure, reliable in use, high in threshing quality and high in production efficiency.