Abstract: In order to explore the method of using ultraviolet light and coupled thermal reduction process to prepare RGO/nanoTiO₂ composites under the assistance of ultrasonic and investigate the photocatalytic reduction performance in the anoxic water, graphene oxide (GO) was prepared by improved Hummers method using flake graphite as raw material, and reduced graphene oxide (RGO) was prepared by ultrasonic/ultraviolet light reduction process firstly. Then, butyl titanate ester and RGO were used as precursors, RGO/nanoTiO₂ composite photocatalytic materials were prepared by the method of sol-gel and high temperature heating under nitrogen protection. After that, the structure and properties of RGO/nanoTiO₂ composites were characterized by FTIR, XRD, BET and ultraviolet-visible spectroscopy. Finally, 2,4-dichlorphenoxyacetic acid (2,4-D) was used as probe, the photocatalytic properties of RGO/nanoTiO₂ composites in anoxic water and the degradation mechanics of 2,4-D were studied. The results show that less reactive groups are generated on six carbon ring of GO when adopting the Hummers method of low temperature oxidation, the rings structure can be well repaired by using ultrasonic/ultraviolet light reduction process and the coupled high temperature thermal reduction process. The prepared RGO/nanoTiO₂ composites have good performances of 2,4-D degradation, under the anoxic condition, 2,4-D mainly conducts photocatalytic reduction reaction, the chlorines on benzene ring are removed and produces middle products such as chlorophenol, pyrogallol, phloroglucinol and so on, part of the 2,4-D is oxydative degraded to generate CO₂ and H₂O. The obtained conclusions indicate that the prepared RGO/nanoTiO₂ composites have good photocatalytic reduction performances.