Abstract: According to the experimental study on a 1/2.5-scaled model of two-span and three-story middle frame composed of reinforced concrete beams and lattice steel reinforced concrete (SRC) special-shaped columns under reversed loading,the elasto-plastic feature,integral and inter-story lateral stiffness degradation of the structure were analyzed. The test results indicate that the lattice steel reinforced concrete middle frame has uniform vertical stiffness,the degradation of which shows a fast to slow regulation. The relationship between story drift and the ratio of story stiffness degradation was obtained. The elasto-plastic behavior of the structure in positive and negative directions is similar. The ultimate elasto-plastic story drift rotation is larger than the limit value specified by the code,indicating the high capacity of collapse resistance. Compared with the reinforced concrete frame with special-shaped columns,the ductility of lattice SRC frame structure is better. The failure mechanism of the structure is the beam-hinged mechanism,satisfying the seismic design principle of “Strong Column and Weak Beam”.