Seven RC bridge decks that have been used for nearly 60 years were tested on flexural behavior after being strengthened with steel plates and composite steel plates and CFRP. The flexural capacity，stiffness，cracks and strain，as well as the failure modes of the test slabs under different strengthening methods were compared and analyzed. The results show that both steel-bonded reinforcement and composite reinforcement of steel plate and CFRP can effectively improve the flexural behavior of the test slabs. The flexural capacity of the specimens with 2 mm，4 mm，and 6 mm thick steel plates is increased by 52.5%，126.0% and 162.5%，respectively. Correspondingly，the flexural capacity of the specimens with composite strengthened slabs is increased by 87.0%，148.0% and 158.5%，respectively. When the steel plates and CFRP were combined to strengthen the existing damaged flexural members，the strengthening effect of CFRP can be brought into full play. The current codes and regulations for steel-bonded reinforcement can be used for the calculation of flexural capacity of existing damaged RC slabs. A calculation method for flexural capacity of existing damaged members strengthened by steel plates and composite steel plates and CFRP considering damage effect is proposed，and the calculated results agree well with the experimental results.