The interfacial bond strength between CFRP（carbon fiber polymer）and concrete is an important factor for bending properties of CFRP-concrete composite beam．Three groups of numerical models are established based on the different bond length and interfacial strength ．Four-point bending loading processes controlled by displacement are simulated．Influence of Interface Strength on Bending Properties of CFRP-concrete beam has been discussed．The results show that the interface strength has little effect on the macro-bearing capacity and the stiffness of composite beams pre-cracking，but significant effect on stiffness and ductility after cracking，and it also reflected that the longer CFRP is stuck，the more sensitive to the changes of the interfacial strength．