The central hub radial support structure of primary mirror in large aperture telescope is analyzed. A kind of central hub with an expanding ball has been designed, and its capability in different aperture mirror and situation is demonstrated. It has been used in mirror support structure, and can efficiently restrict two displacement degrees in the plane perpendicularly to the optical axis. At the same time, it cooperates with the axial and radial support of primary mirror, which can bear partial weight of primary mirror and guarantee the deformation accuracy of optical surface. The central hub strcuture can also accommodate different temperatures of environment. The results are successfully applied in some primary mirrors from aperture 300 to 1230 mm.