Phenolic resins exhibit outstanding thermal stability, mechanical strength, chemical resistance, and excellent electrical insulation properties, and is widely used in fields such as rail transit and packaging coatings. To prepare phenolic resins with high strength and thermal resistance, fluorinated graphene (FG-NH4F) was synthesized via a hydrothermal method, and it was synergistically incorporated into the phenolic resin matrix alongside cardanol containing flexible carbon chains, yielding fluorinated graphene/cardanol-modified phenolic resin (PRC-FG). The long carbon chain structure of cardanol effectively mitigated the brittleness of the phenolic resin, while the fluorinated graphene nanomaterial further compensated for the reduced thermal properties introduced by cardanol and enhanced the mechanical strength of the resin. Results indicate that at 10% cardanol and 0.5% fluorinated graphene content, the material exhibits flexural strength and tensile strength of 67 MPa and 55 MPa, respectively, representing 39.5% and 44.7% improvements over conventional phenolic resin. Although the incorporation of cardanol reduced the resin’s residual carbon content and thermal decomposition temperature to 44.5% and 432 ℃ respectively, the synergistic modification with fluorinated graphene elevated the residual carbon content and thermal decomposition temperature to 58.1% and 473 ℃, effectively enhancing the phenolic resin’s heat resistance.