Abstract: C/C composites have significant application value in high-temperature thermal structural fields due to their low density, high specific strength, and excellent high-temperature stability. However, conventional 2D carbon fiber preform-reinforced C/C composites, owing to their layered structural characteristics, suffer from insufficient matrix reinforcement in the interlaminar, inter-bundle, and pore regions, making it difficult to form continuous thermally conductive pathways, which limits further improvement of the thermophysical properties of the material. Introducing graphene is an effective way to improve the thermophysical properties of C/C composites. To solve the problem that graphene is difficult to uniformly distribute inside the 2D needle-punched carbon felt preform, resin-supported graphene oxide (GO) was combined with high-temperature thermal reduction and chemical vapor infiltration densification process to prepare reduced graphene oxide (RGO) modified C/C (RGO-C/C) composites with different GO additions. The distribution of RGO in the carbon felt and its effect on the microstructure and thermophysical properties of pyrolytic carbon were studied. The results show that when the GO mass content is 0.5%, RGO is uniformly distributed on the fiber surfaces. The introduction of RGO alters the deposition behavior of PyC, promotes the formation of highly ordered fine grained PyC, reduces annular cracks, and improves its structural ordering. As the RGO content increases, the thermophysical properties initially improve but subsequently deteriorate. Compared with RGO0-C/C, RGO3-C/C exhibits the best overall performance. At 1 200 °C, the coefficient of thermal expansion decreases by 27.78%, while the thermal diffusivity and z-direction thermal conductivity increase by 37.26% and 53.32%, respectively.