A large number of pure graphene sheets were successfully prepared in the process of preparing non-stoichiometric TiO2 graphene nanocomposites by thermally hydrolyzing suspension from graphene nanosheets and titanium dioxide peroxide complex. Pure graphene nanosheets are made from natural graphite using an ultrasonic processor to generate a high intensity cavitation field in a 5bar high pressure ultrasonic reactor. The resulting graphene sheet has high specific surface area and unique electronic properties, which can be used as a good carrier for TiO2 to improve the photocatalytic activity. The graphene prepared by ultrasound is of much higher quality than the graphene obtained by Hummer's method, where the graphite is stripped and oxidized. Because the physical conditions within the ultrasonic reactor can be precisely controlled, and by assuming that the concentration of graphene as a dopant will vary in the range of 1-0.001%, graphene can be produced in a continuous system on a commercial scale.