Abstract: The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures. A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies, thereby improving its economic feasibility. Although full-system finite element analyses are reliable, they are encumbered by significant time requirements and limitations in covering all possible telescope orientations. Therefore, we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles. To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope, based on a model from SiTian project, we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles. Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position, we derive the results for the tube at any position using geometric relationships. Finally, we calculate the coupling factors and combine these impacts. Furthermore, we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses. The results are in alignment with those acquired through a comprehensive computational approach.