Abstract: This paper deals with carbon(graphite)fiber/aluminum composite materials under the thermal cycling condition, to observe the influence on the tensile strength of composites.It is considered that the strength could be changed by the variation of interfacial bonding caused by the thermal stress of the cycling process.The specimens used werefour kinds of C (Cir) /Al wires, which were fabricated by means of Ti-B (CVD) coated fibers and infilitrating with liquid Al alloys(Al-Si and LD2).The tensile strength have been measured after thermal cycling treated in temperature range of R.T.to 4500C for various times.The effects of thermal cycling on the tensile strength of composites were discussed with the micrograph of the fracturesurface. It was indicated that the changes of tensile strength wererelated to the changes of interfacial bonding strength, and there was an optimal state of interface bond which corresponds to providing the maximum tensile strength for each composites according to the different constituents and fabrication processes.