Through the axial compression test of eight fiber reinforced polymer（carbon，glass and basalt）confined stub concrete filled square steel tubes（CCFT），this paper reveals the mechanism and the failure model of this kind of composite column. The test results indicate that carbon fiber reinforced CCFT has the highest axial load and best ductility. And the axial load capacity and the ductility increase with the FRP confinement strength. Under the same FRP confinement level, the basalt fiber CCFT has a better ductility than the glass fiber CCFT. A formula for the calculation of bearing capacity of the square CCFT columns is also proposed. The analytically calculated results are shown to be generally in good agreement with the experimental results from this study and other research.