NOVELTY - Preparing large-area graphene based on nickel film annealing and chlorine reaction comprises washing silicon substrate, carbonizing and growing a layer of carbon layer on the substrate, heating, introducing propane and silane, growing 3C-silicon carbide heteroepitaxial film, placing in a graphene growth device, hydrogen etching to remove scratches and defects, removing the compounds generated by hydrogen etching, reacting with chlorine to produce carbon film, depositing a layer of nickel film on carbon film, introducing argon gas, annealing to obtain graphene film, and removing nickel film.    USE - The graphene is useful for manufacturing solar cells and photon sensors.    ADVANTAGE - The graphene has large area, good continuity, smooth surface and low porosity.    DETAILED DESCRIPTION - Preparing large-area graphene based on nickel film annealing and chlorine reaction comprises (i) sequentially washing 4-12 inches silicon substrate using mixed solution of aqueous ammonia and hydrogen peroxide, and mixed solution of hydrochloric acid and hydrogen peroxide; (ii) placing the cleaned silicon substrate in a chemical vapor deposition (CVD) reaction chamber and vacuumizing the reaction chamber until the vacuum level reaches 10-7 mbar; (iii) heating to the carbonization temperature of 900-1200 degrees C under the protection of hydrogen, introducing propane at the flow rate of 30 ml/minute, carbonizing for 5-10 minutes and growing a layer of carbon layer on the substrate; (iv) heating to 3C-silicon carbide growth temperature of 1200-1350 degrees C, introducing propane and silane, growing 3C-silicon carbide heteroepitaxial film for 30-60 minutes, and cooling to room temperature under the protection of hydrogen to obtain 3C-silicon carbide epitaxial thin film; (v) placing the 3C-silicon carbide film in a graphene growth device, opening the heating power supply, heating the reaction chamber to 1600 degrees C, and hydrogen etching to remove scratches and defects on the 3C-silicon carbide substrate; (vi) removing the compounds generated by hydrogen etching; (vii) adjusting the heating power supply voltage, adjusting the temperature of the reaction chamber to 700-1100 degrees C, opening the vent valve, introducing argon gas and chlorine into a mixing chamber, mixing completely, introducing the mixed gas into the quartz tube reaction chamber via a gas passage, and reacting chlorine and 3C-silicon carbide substrate in the reaction chamber for 3-5 minutes to produce carbon film; (viii) placing the carbon film into an electron beam vapor deposition device, and depositing a layer of nickel film of 300-500 nm thickness on the carbon film; (ix) placing the resulting film in a graphene growth device, heating to 800-1000 degrees C, introducing argon gas and annealing for 10-30 minutes to obtain nickel film covered carbon film reconstructed graphene i.e. graphene sample film; and (x) placing the graphene sample film in hydrochloric acid and copper sulfate solution for removing nickel film to obtain large-area graphene material with 4-12 inches.