In order to research the resistance ability to progressive collapse of steel frame structure under the long-term effects of atmospheric environment, a time-dependent corrosion model of steel structure is developed to predict the changes of cross-sectional area and mechanical properties of the members. A classical multi-story steel frame structure in a Class Ⅲ atmospheric corrosion environment is studied and the Pushdown analysis is performed at different stages of its service time. The first peak load factor, the ultimate load factor and the ultimate deformation are used as evaluation indexes for the collapse resistance ability of the structure. The influences of different material parameters on the evaluation indexes are obtained by sensitivity analysis. The variation rules of evaluation indexes with volume loss rate are obtained based on regression analysis. The results show that corrosion causes degradation of the bearing capacity and ductility of the steel frame structure, especially ductility degradation. The degradation of bearing capacity is mainly attributed to the reduction of material strength and cross-sectional area of the members. The degradation of ductility is attributed to the decrease in steel elongation. There is a strong linear relationship between the evaluation indexes and the volume loss rate, which can be used to qualitatively predict the degradation of structural performance.