Fiber reinforced polymer (FRP) composites have been extensively used in strengthening concrete structure in civil engineering because of its advantages of high strength, light quality, good workability and so on. With the further engineering application, the durability issue of FRP strengthened concrete structure has gotten great attentions. Reinforced concrete (RC) structures sometimes can not normally work because durability decreases in exposure environments such as high temperature and humidity, erode of chemical, carbonation, freeze and thaw cycles, and tidal action of seawater. How about the durability of FRP strengthened RC structures in such severe environments? How to carry out durability design for FRP strengthened RC structures in severe environments? These questions must be paid more attention and solved reasonably before FRP is used in such environments. Based on the research background and sponsored by prophase research special item of national great basic research: "durability research of FRP strengthened concrete members in severe environments", experimental researches have been carried out in the dissertation on durability of FRP composite, interface bond durability between FRP and concrete and durability of FRP strengthened concrete cylinders, including the following work:1. Experiment investigation is carried out on tensile performance of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) subjected to the test environments such as carbonation, freeze and thaw cycles and wet and dry cycles in salt solution, the effects of different environmental conditions, exposure time (cycle times), fiber sheet type on durability of FRP composites are studied. Experimental results show that, the tensile strength of CFRP changes slightly under the environmental conditions, elastic modulus increases, elongation decreases a little under wet and dry cycles. The mechanical properties of GFRP show different degrees of deterioration under the three kinds of environmental conditions. The mechanical performance of CFRP is better than that of GFRP in carbonation and freeze and thaw cycles. Anyway, carbonation, freeze and thaw cycles for limited times and wet and dry cycles in salt solution affect slightly on the tensile performance of CFRP and GFRP.2. The effects of carbonation, freeze and thaw cycles and wet and dry cycles in salt solution on the interface bond behavior are studied by normal tensile bonding strength test and shear bonding strength test. Test variables are cycling times of freeze and thaw cycles, cycling times of wet and dry cycles, fiber sheet type and resin type. The effect rules and