Bridges are subjected to long-term deformations in addition to deformations under design loads. In high-speed railway bridges, long-term bridge deformation and potential degradation of materials may adversely impact the operation safety and riding comfort of the railway. While a high-speed railway network is being established in China, it is significant to understand the effects of long-term bridge deformation on track deformation for effective asset management. This study aims to develop an analytical model to investigate the roles of long-term bridge deformations and bridge-track interlayer degradation. Mechanical analysis is conducted to develop a track-bridge deformation model and derive closed-form solutions that can be applied in design and evaluation of high-speed railway bridges. The analytical study is validated against a three-dimensional finite element model, and used to investigate the effects of key parameters (e.g. bridge deformation amplitude, span length, fastener stiffness, and mortar layer stiffness). This study provides a method to quantitatively evaluate track deformation due to bridge deformations and interlayer degradation. With the developed formulae, real-time condition assessment of high-speed railway track can be performed based on real-time monitoring of bridge deformations.