Three large-scale concrete-filled FRP-steel composite circular tubes and a control steel tube were tested to investigate flexural behavior. The effects of FRP and composite with different types of FRP with various ultimate strains were investigated. The study demonstrated the important effect of FRP, and showed that the load-displacement curves of FRP-steel composite tube beams could be divided into four stages: elastic stage, plastic stage, hardening stage and residual stage. An additional decline stage was gained for multi-fiber with different ultimate strains and steel composite tube concrete beams. FRP could increase the ultimate bearing capacity and bring the hardening stage after steel tube yielding, and a certain degree of stiffness would be achieved to avoid the “zero stiffness”. The composite of a variety of FRP could relax fracture failure for the FRP-steel composite steel concrete beams, realized the successive rupture of fiber in batches and changed the failure modes.