Natural exposure test was carried out on carbon fiber reinforced composites in the marine atmospheric environment of the South China Sea for 0.5 a, 1 a, 1.5 a and 2 a. Based on obtained mechanical properties such as tensile, bending and shear strength of the carbon fiber reinforced composite after exposure test, the grey relational analysis method was adopted, and the environmental damage factor Rr was proposed to comprehensively characterize its mechanical property. According to the value of Rr, the grey prediction model GM (1,1) and the natural weathering model with radiation as independent variable were established respectively. The results show that resin matrix degradation thinning, fiber exposure and other aging phenomena occurred under the influence of irradiation and humidity-heat in the marine atmospheric environment of the South China Sea. Micro-crack damage were found on its surface after 2 years of exposure, and its comprehensive mechanical properties (Rr) decreased with aging time. The accuracy of the grey prediction model reached level 1 (good), while the prediction error of the natural weathering model for the mechanical properties of the carbon fiber reinforced composite after exposure for different periods was less than 0.50%, higher than that of GM (1,1).