Abstract: A GFRP tube in which a RC column is filled in is proposed as a new type of composite member. The member consists of an outer tube made of glass fiber reinforced polymer (GFRP), steel bars, and inner concrete. Bending tests were conducted with three specimens to investigate their flexural behavior. Based on the fiber model, a nonlinear analysis was programmed with the wall thickness of GFRP tube, concrete strength and percentage of reinforcement as principal parameters so as to calculate 9 members, thus obtaining the relevant relationship between bending moment and curvature. The results indicated that the bending bearing capacity of the composite members increases obviously with both the wall thickness of GFRP tube and concrete strength. The theory combining failure mechanism with the composite members was introduced separately to give a formula to calculate the bending bearing capacity of such members. Verifying test results showed that the calculation results agree well with test results.