The invention relates to a titanium dioxide (TiO2) nanotube/ graphene composite material and a preparation method thereof. The method includes utilizing graphite as a raw material, conducting oxidizing and peeling to obtain graphene oxide stably dispersed in solution, conducting suction filtering and drying to obtain graphene oxide powder, stirring TiO2P25 nanometer particles, alkali liquid and alcohol organic solvent in mixing mode, then adding the the graphene oxide powder into the mixture to be dispersed, delivering obtained mixed liquid into a reaction kettle, conducting closed reaction, conduct cooling to the room temperature, conducting separation to obtain white precipitate and conducting washing and burning to obtain the TiO2 nanometer/ graphene composite material. The TiO2 nanometer/ graphene composite material is high in solar energy utilization ratio, free of self particle agglomeration and free of re-accumulation of graphene slice layers. Simultaneously, raw materials are easy to obtain and low in cost. The preparation process is simple and safe. The material has potential application value in the fields of electrode materials, photocatalysis, solar energy splitting water, solar cells, environment and the like.