Experimental research on using MgO expansion agent self-stressing concrete-filled steel tube subjected to axial compressive loading is carried out.The effect of initial self-stress tube on the ultimate strength and deformation capacity is discussed.The experimental results indicate that the self-stress can make concrete core compressed in three directions by restraint of steel tube,enhance the ultimate strength of composite columns subjected to axial compressive loading,delay the expansion of crack of concrete core during elastic-plastic stage and increase the tangent elastic modulus of concrete core.Meanwhile,the self-stress can make the concrete core more compact and resolve the problem of interface disengaging successfully so that it can ensure the concrete core and steel tube act together in resisting the axial load.