Abstract: A series of TiO₂ and TiO₂/graphene nanocomposites (TiO₂/RGO) were prepared by the hydrothermal method, in which Ti(SO₄)₂ was used as precursor. The crystal phase, microstructure and dispersion of TiO₂ in the prepared nanocomposites were characterized by XRD, SEM and TEM. The as-prepared nanocomposites were found to be of visible light response by means of UV-vis spectra analysis. The prepared TiO₂/graphene nanocomposites showed higher photocatalytic activity in degradation of methyl orange under visible light irradiation than that of pure TiO₂. The results showed that TiO₂/graphene nanocomposites, which was prepared by hydrothermal method at 200℃ for 24 hours, exhibited the highest photocatalytic activity under the present conditions. Under visible light irradiation, the degradation rate of 12 mg/L methyl orange solution reached up to 99.9% within 3 minutes over 1 mg/mL TiO₂/RGO photocatalysts.