Abstract: For the steel tube confined concrete (STCC) column-RC beam frame connected by reinforced concrete (RC) ring beam subjected to combined vertical and horizontal loads, there may be a very narrow gap between the ring beam and the column at certain height. The gap has influence on the frame stiffness. By finite element analysis (FEA) of the beam-column joints, the rotation stiffness and the equivalent beam width of the ring beam connector are examined, and the influence factors are investigated. It is found that the ring beam and the frame beam width have significant influence on the rotation stiffness and the equivalent width. Static and pseudo-dynamic tests on a two bay-two story STCC column-RC beam space frame with RC ring beam connectors have been performed. The test results are compared with the analysis results of a 3-bay 10-story frame. It is shown that treating the STCC column- RC beam as rigid joint is reasonable during the analysis of STCC column-RC beam frame connected by RC ring beam.