Static tensile loading experiment and nonlinear finite element analysis were carried out to study mechanical properties and failure modes of diaphragm-through joints of concrete-filled square steel tubular column.With comparison between experimental data and finite element analysis results such as load-displacement curves and bearing capacity,the feasibility of finite element analysis was proved.For diaphragm-through joints of concrete-filled square steel tubular column,it was found that tensile load from steel beam flange was mainly shared by square steel tube and diaphragm; as well as 3 failure modes which were steel beam flange fracture,weld fracture and joint broken.For steel square tube,plastic zone appeared around intersections between steel square tube and diaphragm. However,for diaphragm,plastic zone appeared along the cross-section lines enclosed by steel square tube.