Three kinds of nanofillers (g-C3N4, WS2-g-C3N4 and CNT-WS2-g-C3N4) were synthesized via a facile calcination method, on the basis of which ultrahigh-molecular-weight polyethene (UHMWPE) nanocomposites with the addition of nanofillers were prepared via a hot-pressing method. The effects of g-C3N4, WS2-g-C3N4 and CNT-WS2-g-C3N4 on the microstructure, mechanical and thermal properties of UHMWPE were investigated via X-ray diffraction, nanoindentation and thermogravimetric analysis-differential scanning calorimetry. The tribological performance of UHMWPE and their composites was evaluated via SRV-IV. The wear mechanisms were also analyzed by scanning electron microscope. The results showed that the thermal stability of the composites increased with the addition of a nanofiller, but their crystallinity decreased. The hardness of the composites enhanced in the increased order of WCN/UPE, CN/UPE and CWCN/UPE. The fillers led to a denser crystalline structure of the UHMWPE. Nanofillers were beneficial for reducing the friction coefficient and improving the wear resistance of UHMWPE. Thereinto, CWCN/UPE composite exhibited the lowest friction coefficient and wear volume loss on account for the formation of transfer film on steel ball.