Abstract: To completely investigate aseismic behavior of composite beam-CFST(concrete filled square steel tubular) column frame structures,parameter analysis of the typical 15-story frame structure is conducted.The effect of the parameters,such as steel ratio of the column section,thickness of the floor slab and height of the steel beam on the seismic behavior of the structure is discussed.The analytic results show that the height of the steel beam has the most notable effect on the period and elastic displacement of the structure,and the steel ratio of column section takes the secondary place.And with the increment of the height of the steel beam and the steel ratio of the column section,the period and the elastic displacement of the structure decrease in different degrees.The effect of the floor thickness on the initial stiffness and the ultimate bearing capacity is the most remarkable and the effect of the height of the steel beam takes second place.With the increment of the thickness of the floor slab and the height of the steel beam,the initial stiffness and the ultimate bearing capacity of the structure are increased in different degrees.The height of the steel beam has the greatest effect on the elasto-plastic displacement of the structure.And when the height of the steel beam is increased,the elasto-plastic displacement of the structure is reduced remarkably.According to the results of the parameter analysis,we have a simple and intuitionistic impression on the effect of different design parameters on the seismic behavior of the structure.So during the design course,design parameters can be adjusted pertinently,based on the results of the parameter analysis,which makes the optimization of structure design more quick and exact.