Abstract: Based on the experiments of concrete-filled square steel tubular column connections with interior or exterior diaphragms under cyclic loading,3-D nonlinear finite element models were used to analyze the mechanical properties of these two types of connections using ANSYS.Based on appropriate material stress-strain relations and failure criteria,finite element analyses were conducted under monotonic loading and cyclic loading.The load-deflection curves and shear force-deformation curves by finite element analyses show good agreement with those of the experiments.Parametric analyses were conducted on the connections with exterior diaphragms to investigate the influences of compression ratio,width to thickness ratio,strength of the concrete in the square steel tube and concrete slab height.It is found that compression ratio and width to thickness ratio are more important to the connections.