In order to study the hygrothermal aging process and mechanism of carbon fiber reinforced polyphenylene sulfide (CF/PPS) composites, unidirectional CF/PPS composites were prepared for carrying out hygrothermal aging tests. The chemical structure, crystallization performance, mechanical properties, cross-sectional morphology, heat resistance of CF/PPS composites were tested and the service life was predicted under two humidity conditions: 90 ℃ and 100% RH (immersion and boiling), and 90 ℃ and 80% RH. The results show that the CF/PPS composites after hygrothermal aging do not undergo obvious chemical property changes. Only the plasticization of PPS during the hygrothermal aging process and the performance deterioration caused by moisture exist. The study of microscopic morphology further reveals microcracks, resin deterioration and the interfacial aging process between resin and fibers. The actual service life of CF/PPS composites when serving in an environment of 22 ℃ and a relative humidity of 75% is approximately (69.75 ± 39.05) years.