Abstract: The tolerance of the space thermal cycle effect is one of the important factors that affect the service life of carbon/epoxy composite materials. This paper focuses on the effect of the thermal cycle on a kind of carbon/epoxy composite materials M40/648 (which is composed of M40 carbon fiber and 648 epoxy resin). The temperature range is from -150℃ to +150℃. The mass loss rate, the interlaminar shear strength, the surface morphology and the composition are investigated. It is indicated that the thermal cycle can lead to a mass loss of 0.04%-0.07%. The interlaminar shear strength is increased in the case of 200 temperature cycles. In contrast, with 300 cycles, the interlaminar shear strength is decreased by 1.16%. The composite materials display an obvious change of the fracture morphology along with the decrease of the surface C element content.