Abstract: An experimental study was conducted to determine the effects of thermal cycling on the atomic oxygen reaction with carbon-reinforced resin-matrix composites. Two types of materials were selected for this study and they are M40/DEA-1 and M40/AG-80. The calculation results of the atomic oxygen reaction rate and the interlaminar shear performance test indicate that the thermal cycling of certain cycles within a certain range may enhance the atomic oxygen resistance of the materials. In this study, the X-ray photoelectron spectroscopy (XPS) and the scanning electron microscopy (SEM) are used for the surface morphology and component analyses. The analyses have revealed the effects of the thermal cycling on the atomic oxygen reaction with carbon-reinforced resin-matrix composites.