Abstract: It has been studied and simulated that 6 pure bending of concrete-filled steel tubular members with the ratio of width and thickness being greater than 55. It has also been studied that the forced behavior and influencing factors of the steel tube concrete beams. The study results show that the concrete-filled steel tube bending members have high flexural capacity and good ductility. Even the cross-section deflection reached L/20, the load of the specimen on the outside can still increase. The effect of ratio of width and thickness is more significantly than that of the ratio of height and width on the flexural capacity of the member. It has been adopted SAP 2000 to simulate the forced full process of the steel tube concrete beams, whose result agreed well with the test result.