Abstract: Given the widespread use of cable vibration acceleration data in railway bridge health monitoring systems for calculating the average cable forces, an approach that fails to assess cable fatigue life, this study introduces the synchrosqueezing transform to address this issue. Building on the explicit relationship between cable vibration frequency and cable forces, the method enables time-varying cable force estimation for railway cable-supported bridges under low-frequency acceleration sampling conditions. Field validation is conducted on two cable-stayed bridges under construction, demonstrating its applicability to both parallel-wire cables and steel strand cables. For the first time, a fatigue damage assessment and life prediction methodology is proposed for cables and hangers in cable-supported railway bridges, incorporating corrosion effects (cable and anchorage systems), S-N curve parameter variability, and external load randomness. Using the health monitoring data from two in-service rail-cum-road bridges with the main spans exceeding 1 km, fatigue life evaluations are performed for suspension bridge hangers and cable-stayed bridge cables. Key findings include: Fatigue life of both hangers and cables decreases rapidly with corrosion. Under corrosive conditions, stay cables typically reach failure within 30 years of service, whereas suspension bridge hangers exhibit fatigue lives significantly exceeding the 30-year design service life, showing lower susceptibility to corrosion-fatigue failure. Stay cable failures are primarily driven by corrosion-fatigue mechanisms, with longer cables demonstrating substantially shorter fatigue lives than shorter ones. Fatigue life of side-span cables is notably lower than that of mid-span cables, necessitating prioritized inspection and maintenance focus on long cables and side spans. The variability of S-N curve parameters exerts far greater influence on fatigue life than external load fluctuations. For railway bridges under stable operational loads, monitoring S-N curve parameter shifts due to corrosion is critical.