To meet the requirements of modern railway bridge emergency repair, a technical scheme for a deployable medium-span emergency repair girder based on telescopic diagonal web members is proposed. The girder utilizes deployable frame units as its basic components, enabling folding and deployment through the extension and retraction of the diagonal web members. This design resolves the technical challenge of balancing assembly efficiency with storage and transportation space in existing repair girders, while also meeting the emergency repair demands of both conventional-speed and high-speed railway bridges. Finite element analysis models and multi-body dynamics models are established to conduct static analysis and vehicle-bridge coupled dynamic response analysis on the deployable railway emergency repair girder. The results indicate that the stress levels and displacements of the deployable repair girder meet the limit requirements of the “Code for Design on Railway Bridge and Culvert”. The member stresses are highest under the loading of mixed passenger and freight railway traffic. The arrangement of the diagonal web members significantly influences the ultimate bearing capacity of the deployable girder, with the inverted V-shaped configuration yielding a higher ultimate bearing capacity. Among the three truss configurations for the 32 m span, the heavy truss emergency repair girder exhibits superior dynamic response indices. The wheel load reduction rate is identified as the key factor controlling train speed, and the speed limit for high-speed trains crossing the 32 m span deployable railway emergency repair girder can be controlled at 120 km · h^-¹.