Abstract: TiO2/g C3N4 composite photocatalyst with visible light response was synthesized by the solvothermal method, and then the as synthesized photocatalyst was protonated. The samples were characterized by X ray diffraction(XRD), nitrogen absorption desorption, scanning electron microscope(SEM), transmission electron microsope(TEM), Fourier transform infrared spectrometer (FT IR), UV vis diffuse reflect spectroscope(UV vis DRS) and photoluminescence spectra (PL). The photocatalytic performance of the TiO2/g C3N4 was evaluated by the degradation of methylene orange (MO) under the visible light. The results show that porous TiO2 nanocrystalline and g C3N4 are able to form “sesame cake” composite structure. The absorption edge of TiO2/g C3N4 photocatalyst expands to 465 nm, which appears remarkable red shift compared with TiO2. The coupling of TiO2 and g C3N4 with suitably matching band level of conduction and valance bands provides TiO2/g C3N4 photocatalyst with the driving forces to separate and transfer photogenerated electron hole pairs. The protonation process can improve the absorption of visible light, increase electronic transfer ability and enhance the TiO2/g C3N4 photocatalyst activity.