The pointing accuracy of radio telescope is usually less than one-tenth of the main beam width. For large-caliber antennas with the short centimeter-band or millimeter-wave band, the pointing accuracy must be as high as several arc seconds. Therefore, for large-diameter and high-frequency reflective antennas, the pointing problem has become an important focus of antenna performance. Among many structural subsystem factors that affect the antenna pointing accuracy, little research has been done on the deformation factor of the main reflecting surface. Based on the structural characteristics of the antenna, a spatial coordinate system of the reflecting surface is established in this paper. Based on the spatial coordinate values of the principal surface points after deformation, a non-linear least squares fit method with 3 degrees of freedom is proposed to accurately predict the antenna pointing. Finally, the spatial geometric relationship is used to strictly derive the precise adjustments of the pitch and azimuth for the correction of the pointing error of the antenna, and the indirect relationship between the deformation of the main surface and the pointing error is constructed. This has certain guiding significance for improving the pointing accuracy of large radio antennas.