Abstract: The sol-gel process and structure of monolithic TiO2 aerogels were experimentally studied. It has been shown that, the increasing of the catalyst and precursor amounts can both lead to shorter gelation time and the hardness improvement of the wet gel, while they lead to a decrease and few change in the wet gel transparency, respectively. The gelation time, the transparency and hardness of the wet gel vary in the parabolic manner. The aerogels of different densities prepared with different catalyst amount were characterized by scanning electron microscopy. The reaction degree of polycondensation is found to increase with the increase of the catalyst and precursor amounts, the degree of cross linking of the aerogel colloid particles also increases, and no ≡C—O bond exists in the aerogels b