Abstract: To address the issue of the large-span （24 m width） steel keel structure of the CAVE screen in the Mogao Grottoes, firstly, a modular theory is adopted to design a model of the CAVE screen steel keel structure; Secondly, finite element simulation analysis was conducted on the top foundation ring support using the built-in simulation module of Solidworks. The results showed that the stiffness and strength of the top foundation ring support met the design requirements; Finally, after on-site installation and 3D laser scanning, the results showed that the designed large-span CAVE screen steel keel structure meets the actual needs. It is feasible to adopt modular design for large-span CAVE screen steel keel structure.