The mechanical behavior of rigid frame tied-arch bridge was studied on the basis of 3D finite element analysis and 1∶3 scale model test of pier-arch joint. The mechanical behavior of the prestressed concrete beam separated from the tie bar is similar to continuous beams supported by elastic supports, and is better than that of general tied-arch bridge. However, the mechanical behavior of the arch is similar to that of general tied-arch bridge. Pier-arch joint is the key part of rigid frame tied-arch bridges. Because enough studs and PBL shear connectors are arranged, and enough prestress is used, the pier-arch joint of Yongxiu Bridge has enough margin of safety and can transfer forces smoothly. The application of rigid frame tied-arch bridge on passenger dedicated railway is feasible.