The invention discloses a graphene / inorganic semiconductor composite film and a preparation method thereof. The preparation method includes using graphene oxide or reducing graphene and inorganic semiconductor precursor as major raw materials, using a sol-gel method method or hydrothermal / solvent thermosynthesis method, using a function group on the surface of graphene as a nucleating point, and using the nucleating point to control size, shape and crystallization performance of an inorganic semiconductor to prepare an even composite film. Hydrogen bond, ion bond or covalent bond is formed by the prepared composite film using the function group on the surface of graphene with the inorganic semiconductor, dispersibility between graphene sheets is increased by the inorganic semiconductor, surface defects of graphene are compensated, conductivity and uniformity of graphene are increased, interface geometric contact and energy level matching of graphene and semiconductor nano-particles are improved, application range of a device is enlarged, and the graphene / inorganic semiconductor composite film is suitable for photoelectric fields of solar cells, sensors, OLEDs (organic light emitting diodes), touch screens and the like.