The photocatalytic depolymerization of Dagang vacuum residue (DVR) was carried out with H2O2 over TiO2 in a photochemical reactor. Most of the organic matter in DVR was converted into oxygen-containing organic compounds. The yields of carboxylic acids, oxalates, epoxy compounds, and hydroxyl compounds from DVR oxidation are 40.6%, 36.4%, 17.86%, and 13.5%, respectively. In addition, the oxidation causes significant decrease in viscosity and chromaticity of DVR. The related reaction mechanisms are discussed according to the experimental results.