Abstract: Based on the technical specification for structures with concrete-filled rectangular steel tube members, five specimens of new connection-inner and through-type diaphragm subassembly were manufactured. The seismic resistance behavior of connections was studied through cyclic loading tests and parametric analyses were conduced on the connections to investigate the influences of the additional plates to both sides of flanges, the width-to-thickness ratio of the column and the length of the through diaphragm. It is found that the hysteresis curves attained in the experiment are full and show no obvious stiffness deterioration, and the connections have a good energy dissipation capacity; the stress distributing can be ameliorated and the ductility of the connections can also be improved through welding the additional plates to both sides of the flanges. The nonlinear finite element models were also used to analyze the hysteresis behavior of the connections under cyclic loading using ANSYS 8.0. Based on the proper finite element model, the influences of the compression ratio, the concrete strength in the steel tube and the length of the through diaphragm on the mechanism behavior of connections were analyzed. Analytical results show compression ratio and the length of through diaphragm are more important to the connections; the framework curves of the finite element models show good agreement with those of the experiments.