Abstract: Carbon aerogel (CA) spheres were prepared by an inverse phase suspension polymerization of resorcinol and formaldehyde (RF) monomers with hexadecyltrimethylammonium bromide as catalyst. The gelation mechanism of RF gel was investigated by analyzing the changes of viscosity, pH, temperature and the UV spectra of the as-formed sol. Results indicate that the gelation of resorcinol and formaldehyde is a condensation polymerization, which can be divided into four stages including linear condensation, cross-linking, growth of colloidal particles and macroscopic gelation.