Abstract: To study the deformation behavior of large cast iron components, such as machine tool large box-type castings, during the casting and stress-relief processes, a self-developed robotic machining unit's supporting workbench was selected as the research object. Multiphysics field numerical simulation of the entire casting process and regional stress-displacement response analysis is involved. Firstly, the ProCAST software was used to simulate the thermal-mechanical coupling of the casting process, obtaining the equivalent stress distribution and the evolution trend of residual stress at key points. The results show that thermal stress is the primary source of stress, while phase transformation stress and constraint stress have a relatively small effect. Subsequently, modal analysis was conducted through numerical simulation to identify suitable excitation points, frequencies, and excitation forces. This enabled vibration stress relief and validated its effectiveness in reducing residual stress. This process reduces the deformation caused by residual stress release during the operation of the complete machine, improving dimensional stability. Finally, based on the stress distribution in the key regions of the casting and its geometric characteristics, a Python script was used to isolate the residual stress field in specific regions, exploring the effect of local stress release on the deformation of critical functional points. The results show that the deformation response obtained by separately loading each functional region has negligible errors, only 0.069 μm (error less than 1%) compared to the sum of the results from loading all five regions simultaneously, confirming that the deformation induced by residual stress has good linear superposition properties. Furthermore, by introducing the "global average sensitivity" index, the influence of residual stress release in different regions on structural deformation was quantitatively analyzed. The research results provide a theoretical basis for residual stress control in large cast iron components and the selection of regions for stress detection in castings.