The invention discloses a graphene film for light efficient electromagnetic shielding and a preparation method thereof. An oversized graphene oxide sheet is used for forming the film and by virtue of an annealing mode under high temperature, the graphene defect is perfectly repaired, the edge defect is reduced to the lowest to form a perfect large conjugate structure, and the smoothness of a head conducting path of the graphene is guaranteed; furthermore, through three steps of independent warming processes, a functional group is separated from the surface of the graphene step by step, a pore-foaming agent included between the graphene sheets is slowly decomposed, and the functional group and the pore-forming agent are released step by step in a gas mode; and meanwhile, the graphitization process is gradually developed to form a graphene micro airbag; in the forming process of the micro gasbag, the most stable functional group on the surface of the graphene falls off, thereby producing the graphene structure formed by 1-4 layers of graphene sheets with the gas expansion under high temperature; the successful introduction of the graphene few-layer structure greatly promotes the conductivity performance of the material. The micro gasbag structure is assisted by good conductivity performance so that the graphene of the invention has strong electromagnetic shielding performance.