To investigate the structural safety implications of cable rupture on the arch bridge system, this study focuses on an under-construction arch bridge in Shaanxi Province, employing finite element numerical simulations. Various scenarios of "sudden cable rupture" during operation are subjected to dynamic response analysis and safety assessment. Results demonstrate that the combined effects of the pier-beam-arch structure significantly impact adjacent spans while minimally affecting others. Structural vibrations stabilize within 5 seconds post-rupture, with main beam responses exhibiting minor amplitudes compared to larger ones in the arch rib. The maximum dynamic amplification factor (DAF) for the arch rib reaches 10.5, and the demand-capacity ratio (DCR) of hangers substantially increases under dynamic loading. Hanger forces experience a several-fold increase shortly after cable rupture, with a maximum DCR of 40.3%, indicating a significant reduction in structural safety reserves. The potential for consecutive hanger ruptures during cable vibration highlights the necessity for heightened safety vigilance during bridge operation.