Abstract: Taking two pieces of 1 bay and 2 stories models of concrete-filled RHS(rectangular hollow section)frames as research objects,based on pseudo-static test and considering the effect of steel ratio of the column section,it was researched the behavior of concrete-filled RHS frames in the aspects as:destroy character,loading capacity,hysteretic curves,deformation,energy dissipation,degradation of strength and stiffness;also,it was analyzed the effect of steel ratio of the column section on the forced and seismic behaviors;besides each index was compared with reinforced concrete frame and steel frame separately.The result shows that concrete-filled RHS frame has stronger deformation capacity,plumper shuttle shape hysteretic curves,the excellent ductility and enough later loading capacity,because the frames' ductility coefficient reaches 5.56 to 6.80,also the frame can form the beam hinged collapse mechanism,so the mechanical and seismic behaviors of the frame are excellent,which are superior to those of reinforced concrete frames and steel frames,it is deserved researching thoroughly.