This paper provides the results of a study on the connections of Concrete Filled Circular Tubular(CFCT) column to beam by simplified connection models. The internal stiffening is the method which is reinforced by longitudinal ribs or studs bolts attached around the pannel zone between the beam-CFCT column connections. The important parameters of this paper are the infilled concrete and the thickness variation of the column pannel zone. The strength of each connection types are compared with those which are not filled with concrete. The experimental results are compared with those which are analyzed by FEM models.