Carbon fiber was modified in situ by pyrolytic carbon, modified carbon fiber reinforced polyimide matrix composites (PI-C/C_f) were prepared. The heat resistance of the materials was characterized by TGA, static thermal oxygen aging; it is found that the method can effectively improve the heat resistance of the materials, and the initial decomposition temperature is above 540 ℃. Combined with the high temperature wear test of the composite materials, it is found that the wear rate of the materials at 450 ℃ is less than 1×10^-6 m³/mm, which has good high temperature wear resistance. By analyzing the thermal oxygen aging mechanism of PI-C/C_f composites, it is found that the chemical structure of the matrix resin is the main factor affecting the heat resistance of the composites.