Abstract: Concrete- filled thin-walled square steel tubes are becoming more and more attractive to be used in engineering practice, for reasons of saving construction time and costs.However, local buckling is more likely to occur for thin-walled tubes, and thus decreases the lateral confinement on the concrete core.In order to improve the performance of such kind of composite columns, the effectiveness of longitudinal stiffeners welded on the steel tubes has been studied in recent years, which demonstrates the fact that the stiffeners can effectively delay the tube local buckling, and improve the serviceability of composite members.This paper discusses the allowed width- to- thickness ratio of the sub- panels and the rigidity requirement of the stiffeners used in stiffened composite stub columns.To evaluate the feasibility of currently available design codes in predicting the load- carrying capacity of the stiffened composite stub columns, the bearing capacities predicted using those design codes are compared with the currently available test results of adequately stiffened stub columns.