The 11 continuous RC beams strengthened with different FRP are tested under different load history. The results show that the flexural strength, stiffness and anti-crack behavior of the strengthened RC beams are improved. The ultimate load capacity of RC beams strengthened with FRP laminates is related with the initial stress level, and reduces with the increasing of the initial stress level. The ductility of FRP strengthening beams is somewhat lower comparing with RC beams. The ductility of GFRP strengthening beams is better than CFRP strengthening beams, and the negative bending regions of c...