In order to investigate the hysteretic characteristics of beam-to-column composite connections in middle-high strength steel frame,four full-scale composite specimens are subjected to destructive test under the low-cyclic reciprocating load.Then the skeleton and the envelope of hysteretic curve are obtained,and the impact of reinforcement ratio and loading mode on the bearing capacity and ductility of the connection are analyzed.Based on the test results and analysis,the three linear restoring force model of the composite connection in consideration of bearing capacity and stiffness degradation is gained.From the analysis results,it can be concluded that the reinforcement ratio mainly affects the connection ductility;symmetric loading can provide higher initial stiffness and ultimate strength in sagging moment;the restoring force model can be used in elasto-plastic seismic time-history analysis.