<p>The stability of surrounding rock masses in large underground openings remains a critical concern during construction, particularly under high in situ stress regimes and complex geological settings. This study investigates the deformation characteristics of surrounding rock in the main powerhouse of the Yebatan hydropower station through systematic monitoring data analysis and numerical simulation. The results reveal that significant deformations are observed in multiple excavated and supported surrounding rock during subsequent excavation phases of the main powerhouse, which occurred at various locations and exhibit continuous development that persisted throughout the entire excavation period. Notably, the deformation patterns demonstrate pronounced spatial and temporal heterogeneity. Within fault-affected zones, alternating opening and compressive displacements are observed between adjacent monitoring points along the depth of the rock mass. Furthermore, spatial non-uniformity is evident in both displacement growth rates and daily increments of anchor cable load across identical elevations along the powerhouse axis. Moreover, the displacement–time curves at critical positions highlight distinct evolutionary patterns, with marked non-coordinated and time-dependent features emerging during excavation pause periods. Numerical simulations confirm that both stress and displacement in surrounding rock undergo significant alterations during excavation, particularly at fault-exposed locations. When analyzing solely the initial versus final stress states, stress relaxation becomes apparent in shallow rock masses, while stress concentration predominates in deeper formations. Finally, the fundamental mechanisms governing the spatial and temporal deformation characteristics of the surrounding rock are comprehensively analyzed.</p>