Abstract: The C-axis system of the C-arm Digital Subtraction Angiography (DSA) device plays a pivotal role in medical image acquisition, and ensuring that its strength and stiffness meet design requirements is essential for the overall performance of the C-arm. In this study, finite element analysis using ANSYS was conducted on the C-axis system of a domestic C-arm DSA device. The stress distribution and deformation fields of the C-arm structure were analyzed under four extreme working conditions: vertical, parallel, and ±45° tilt. The strength and stiffness of the system were verified, confirming the reliability of the overall structure. To address the issue of insufficient rail contact in the C-axis connection mechanism, the layout of the guide rail assembly was optimized. A simulation of the contact strength on the optimized guide rail surface showed that the maximum contact stress was reduced by 20.88%, effectively lowering the risk of wear-induced failure during long-term operation and improving the operational stability of the equipment. This research provides valuable references for the analysis and optimization design of C-arm systems in similar DSA equipment.