To explore the performance of Corrugated Steel Plate - Composite Beam Structure, based on an old bridge reinforcement engineering located in Hunan province, an equivalent rectangular beam numerical model was established through equivalent stiffness method, and the method of stress conversion was discussed. The properties of Composite Beam Structure under vehicle loads and construction period were analyzed by using equivalent numerical model. It is found that equivalent rectangular beam model can be used to analyze Composite Beam Structure, stress of equivalent rectangular beam can be converted to stress of Composite Beam Structure by the formula of this paper, stress of most points are the same except for the boundary of structure; the most unfavorable condition occur in the double rear axle symmetry acting on the vault, bending moment and axial force of structure is maximum in this condition, which need to be considered when calculated internal forces of structure under live loads; Composite Beam Structure has high construction speed, about 4~5 months construction period, the most unfavorable situation during the construction is the eccentric loading situation during backfilling, moment of structure is maximal and axial force is minimal at this time. At the end of construction, axial force of structure is maximal. These two conditions during the construction process cannot be ignored; CHBDC method is not suitable to calculate internal forces of Composite Beam Structure, which should be analyzed by other methods.