In aqueous solutions containing basic catalysts, a wet gel was synthesized through the sol-gel process of resorcinol (R) and formaldehyde (F), The formation of RF gel is dependent on the ratio of R and catalyst (C), density of solid fraction, and temperature. The gelation proceeded quickly with low R/C ratio, high density, and high temperature. The RF organic aerogel was obtained from the wet gel by low-temperature supercritical solvent drying with carbon dioxide. The RF aerogel product shows extremely low thermal conductivity and highly specific surface area due to its ultra-porous structure. The thermal conductivity is closely related to the pore size distribution of the aerogel, The aerogel in the solid fraction ranges of near 3% (0.06 g/cm(3)) and the R/C ratio of 300 retains the lowest thermal conductivity.