A co-sol-gel method was used to prepare SiO2-doped TiO2. The amount of ethyl silicate added into the precursor, calcination temperature and time, adsorption equilibrium, and photocatalytic activity of the material were investigated as the factor of degradation efficiency. With the optimum composition of the precursor, the prepared gel calcinated at 500 oC for 3 h showed the highest photocatalytic activity. After 30 min stirring to reach adsorption equilibrium, adsorption contributed less than 2% to the total decoloration of methyl orange on the SiO2-doped TiO2 material. Photocatalytic methyl orange degradation continued with increasing irradiation time. Methyl orange degradation rates after 30 min and 100 min were 31.1% and 96.9%, respectively.