A hybrid sizing agent containing polyamide-imide （PAI）-functionalized carbon nanotubes was prepared， and its effect on the interface aging resistance of carbon fiber/polyamide-imide （CF/PAI） composite materials was investigated. The results show that before thermal aging treatment， the interfacial shear strength （IFSS） and interlaminar shear strength （ILSS） of the hybrid sizing agent-modified CF/PAI composite are increased by 42.5% and 74.0%， respectively， compared to the unmodified CF/PAI composite. After thermal aging treatment， the IFSS and ILSS of the hybrid sizing agent-modified CF/PAI composite are further increased by 15.8% and 20.8%， respectively. Mechanistic studies reveal that the hybrid sizing agent effectively enhance the micro-interface thermal aging resistance of CF/PAI composites through factors such as chemical bonding， mechanical interlocking， and interfacial compatibility. The introduction of carbon nanotubes and the increase in the modulus of the matrix resin during thermal aging further improves the modulus and hardness of the interface region， thereby enhancing stress transfer efficiency and reducing stress concentration， which in turn improves the macro-interface thermal aging resistance of CF/PAI composites.