Abstract: Based on some reasonable hypotheses and the stress-strain relationship of concrete obtained by the “adjusting valid modulus depending on age” method, a compact formula to calculate the conversion elastic modulus of the core concrete is presented, which can consider both the influences of creep and the interaction between steel and concrete. The application of the formula to creep analysis for the concrete-filled steel tubular (CFST) arch bridge can simplify the analysis process. At the same time, the method is implemented for creep analysis of a 308-meter-span CFST arch bridge by the FEM software ANSYS. By comparison, the proposed method is proved to be feasible and relatively precise. At the same time, the creep effect on structures is compared regarding the two different creep coefficient models recommended by the new and old bridge design codes.