Method for preparing graphene film

The invention discloses a method for preparing a graphene film, which comprises the following steps of: putting oxidized graphite or expandable graphite into a heating furnace, then quickly heating the graphite to the temperature of between 700 and 1,500 DEG C, maintaining the temperature for 0.5 to 30 minutes, naturally cooling to obtain flocculent graphite, directly grinding a certain amount of flocculent graphite into powder, putting the powder into a beaker filled with liquid, standing or stirring or ultrasonically treating the solution, and then standing the solution for certain time to form the graphene film on the liquid level. In the method, the graphene obtained by high-temperature reduction and oxidation of the graphite is used as a film forming raw material and has the advantages of good reduction effect and good film electrical conductivity; and meanwhile, the very thin film is obtained by using mutual effect between the graphene and the surface tension of the liquid, and has very good transparency.