Abstract: The mechanical properties of CFST arch bridges tend to change and lose their bearing capacity at high temperature. In order to seek reasonable fire protection design method, Studing on mechanical behavior under fire of concrete filled steel tubular arch bridge is studied with ANSYS thermal analysis model. Rationality of ANSYS thermal analysis model is verified by the comparison between numerical simulation and experimental data. On this basis, the influence of suspender fire on the deck, arch rib shape and suspender internal force of CFST arch bridge is analyzed. Result shows that deck deformation and suspender axial force within fire Boom 30 m cannot be ignored. The study can provide reference for fire protection design and rehabilitation for such bridges.