Monolithic polymer(resorcinol-formaldehyde) reinforced alumina (RF/Al 2 O 3 ) aerogel composites were prepared using a sol-gel method and supercritical fluid CO 2 drying. The formation mechanism, chemical compositions, pore structures, morphologies, thermal and mechanical performances of RF/Al 2 O 3 aerogel composites with different RF/Al molar ratios were investigated. The results show that the two networks of organic resorcinol-formaldehyde and inorganic alumina are completely independent of one another. The as-synthesized RF/Al 2 O 3 aerogels consist of spherical organic carbon particles and fibrous alumina, which possess low bulk density (0.077-0.112 g cm -3 ), low shrinkage (1.55-2.76%), low thermal conductivity (0.024-0.028 W m -1 K -1 ), and high specific surface area (453.26-722.75 m 2 g -1 ). Especially, the sample prepared with molar ratio RF/Al = 1 shows the best network structure with the higher compressive strength (1.83 MPa) and Young's modulus (122.57 MPa). The resulting robust RF/Al 2 O 3 aerogel composites could be potentially used as thermal insulators, catalysts and adsorbents.