A novel hybrid of carbon nanotube-supported graphitic carbon nitride (g-C3N4/CNT) was firstly fabricated via facile calcination method, and then filled into poly (phthalazinone ether sulfone ketone) (PPESK) to prepare self-lubricating composite film. The microstructure and chemical composition of g-C3N4/CNT hybrid were characterized, and its enhancement on the tribological properties of PPESK was investigated by comparing to pure PPESK and its composite films with g-C(3)N(4)or CNT only. Results showed that g-C(3)N(4)wasin situattached to CNT surface uniformly, which favored for improving the physical and chemical interfacial interaction between fillers and PPESK. Besides, by the incorporation of g-C3N4/CNT, the hardness and elastic modulus of PPESK were improved by 15.05% and 41.75%, respectively. More importantly, PPESK-g-C3N4/CNT composite film showed the best tribological property among PPESK composite films. Its friction coefficient and wear rates were 65.5% and 84.1% lower than those of pure PPESK, as a result of good dispersion and interfacial action, as well as synergism between CNT and g-C3N4. Based on the worn surface analysis, the enhancement mechanism of g-C3N4/CNT was proposed.