NOVELTY - A titanium dioxide/graphene composite photocatalyst is prepared by taking tetrabutyl titanate, graphene oxide, concentrate acid and deionized water; dissolving graphene oxide in organic solvent, and ultrasonic dispersing for 1-3 hours to obtain graphene oxide dispersion solution; adding tetrabutyl titanate to graphene oxide dispersion solution, ultrasonic treating for 30-60 minutes, adding concentrate acid, ultrasonic treating for 30-60 minutes, gradually dripping deionized water and ultrasonic treating for 30-60 minutes to obtain sol; and reacting sol in reaction kettle, drying and grinding.    USE - Method for preparation of titanium dioxide/graphene composite photocatalyst. The titanium dioxide/graphene composite is used as photocatalytic material, solar battery material, and lithium ion battery cathode material.    ADVANTAGE - The method solves technical problems of prior art for preparing titanium dioxide/graphene composite photocatalyst which has large titanium dioxide grain size and low photocatalysis efficiency. The prepared photocatalyst has titanium dioxide grain size of 5-10 nm. It can be applied to catalyze degradation of methyl orange by visible light, where degradation within 2 hour can be 75%.    DETAILED DESCRIPTION - Titanium dioxide/graphene composite photocatalyst is prepared by:    (A) taking tetrabutyl titanate, graphene oxide, concentrate acid and deionized water;    (B) dissolving graphene oxide in organic solvent, and ultrasonic dispersing for 1-3 hours to obtain graphene oxide dispersion solution;    (C) adding tetrabutyl titanate to graphene oxide dispersion solution, ultrasonic treating for 30-60 minutes, adding concentrate acid, ultrasonic treating for 30-60 minutes, gradually dripping deionized water, and ultrasonic treating for 30-60 minutes to obtain sol; and    (D) transferring sol to hydrothermal reaction kettle, reacting for 4-24 hours at 120-200 degrees C, washing reactant with absolute ethanol, cleaning with deionized water, vacuum drying at 40-60oC for 8-24 hours, grinding to obtain titanium dioxide/graphene composite photocatalyst.    Mass ratio of tetrabutyl titanate to graphene oxide is 1:0.001-0.03. Volume ratio of tetrabutyl titanate to concentrate acid is 15:0.5-2. Volume ratio of tetrabutyl titanate to deionized water is 15:1-3. Concentrate acid is hydrochloric acid having mass percentage of 36-38% or nitric acid having mass percentage of 65-68%.