Abstract: Polyaryletherketone (PAEK) resins with different crystallinities (PAEK-CL, PAEK-CH) and their carbon fiber-reinforced composites (CF/PAEK-CL, CF/PAEK-CH) were prepared by controlling cooling rates to investigate the effects of hygrothermal aging. Results demonstrate that hygrothermal aging reduces the glass transition temperature through water plasticization while maintaining stable crystallinity. Regarding mechanical properties, the elastic modulus of PAEK resins exhibits excellent stability, with tensile and flexural properties varying within approximately 3%. However, the impact strength of PAEK-CL resin decreases significantly from approximately 169 kJ/m² to 14 kJ/m². Furthermore, the interfacial shear strength (IFSS) of CF/PAEK composites is markedly reduced (approximately 13% for CF/PAEK-CL and 33% for CF/PAEK-CH). Nevertheless, due to synergistic effects of multiscale failure mechanisms in interlaminar structures, the interlaminar shear strength (ILSS) maintains exceptional stability. Leveraging the physical entanglement characteristics of thermoplastic molecular chains, composites manufactured via secondary thermal bonding exhibit only an approximately 2% reduction in ILSS under hygrothermal conditions, validating the applicability of their reprocess ability in demanding environments.