A secondary mirror mount in a large telescope introduces different attitude errors at different elevations， reducing the accuracy of the imaging device. In particular， large SiC telescopes suffer from this problem. Without correction of the secondary mirror attitude, a large error of imaging point position was introduced that result in an overload of the precision tracking system. By considering the optical design parameters of the telescope， a secondary mirror correction method based on the coma-free point （CFP） and center of curvature was developed. Stewart platform is used to correct the attitude of secondary mirror based on the telescope elevation. The alignment error before the precision tracking system is reduced from 12.85″ to 1.80″，as a result of the attitude correction of the secondary mirror. The correction method is simple and effective， allowing for coarse alignment of the precision tracking system and preserving the accuracy of the imaging system.