Graphite-based composites are well recognized as ideal functional materials in mechanical seals, bearings of canned pumps, and electrical contact systems because of their outstanding self-lubricating ability, thermostability, and chemical stability. Working in harsh conditions is a huge challenge for the graphite materials, and their tribological properties and wear mechanisms are not well studied. In this study, the tribological performance of metal-impregnated graphite, resin-impregnated graphite, and non-metal-impregnated graphite under high temperature and high load are studied using a ball-on-disc tribometer. The results show that the metal-impregnated graphite (Metal-IG) has a stable friction regime and exhibits better anti-friction and anti-wear properties than that of resin-impregnated graphite (Resin-IG) and non-impregnated graphite (Non-IG) under extreme pressure (200~350 MPa) and high temperature (100–350 °C). The Metal-IG and Resin-IG can reduce the wear depth by 60% and 80%, respectively, when compared with Non-IG substrate. The impregnated materials (metal or resin) can enhance the strength of the graphite matrix and improve the formation of graphite tribofilm on the counterpart surfaces. Friction-induced structural ordering of graphite and slight oxidation of metal in the formed mechanically mixed layer is also beneficial for friction and wear reduction. This study demonstrates the tribological characteristics of impregnated graphite under harsh conditions and provides the experimental basis for the advanced usage of high-reliability and self-lubrication graphite composites.