The photodetector based on Graphene/TiO2 heterostructure is fabricated on the substrate of Si wafer, which takes advantage of the light absorption and surface passivation of TiO2 film. The intrinsic photo-response of the photodetector is investigated in a wide range of wavelength. The result indicates that the graphene field-effect transistor photodetectors passivated with TiO2 film deposited on graphene can efficiently prevent the surface channel absorbing the gas molecules, which reduces the dark current drift of graphene field-effect transistor devices. Meanwhile, the graphene channel is sensitive to the changes in charge, and wide spectral absorption characteristics of the composite film can increase the responsivity of graphene field-effect transistor detector significantly. At the ultraviolet band, the photon-generated carries produced by TiO2 layer are mostly injected into the graphene channel, which leads to obvious n-type doping and the highest responsibility of 3.5×105 A/W. On the other side, at the visible band the impurity level between graphene and TiO2 can improve the carrier lifetime of channel compared with the intrinsic graphene. In contrast with the traditional TiO2 arrays photodetectors, the Graphene/TiO2 heterostructure devices have obvious advantage on the performance of response waveband and responsibility.