The invention discloses a mechanical support structure for a chair. The mechanical support structure includes a hollow shell and a seat, the interior of the hollow shell is of a hollow structure, a movable space is formed, a group of cylindrical blocks with an iron core inside is fixed at the top, in the movable space, of the hollow shell, a group of coils is twined on the surface of the iron core, and a wire through hole structure is arranged on the position, where the coils are located, of the side face of the hollow shell. According to the mechanical support structure for the chair, electromagnetic action is adopted to serve as a main driving medium for adjusting the mechanical support structure, and the controllability is relatively high; besides, the interaction between electricity and magnetism is adopted, a support force can be effectively provided, and buffer action is provided at the same time, so that buffing-type support is achieved; because the interaction force between the electricity and the magnetism is an electric-field force, the leakage phenomenon cannot occur, so that the service life is relatively long; besides, the mechanical support structure can prevent the seat from rotating freely and improve the fitness of the mechanical support structure for people.