▎ 摘　　要

NOVELTY - A method for preparing a graphene sheet by using a supercritical fluid intercalation step and a microwave expansion step, comprising: providing graphite oxide or expandable graphite; performing a supercritical fluid intercalation step, wherein the graphite oxide or the expandable graphite and the urea aqueous solution are intercalated by a supercritical fluid, and then stir by nitric acid with ultrasonically oscillated and filtered. The urea nitrate intercalation graphite can be obtained. Finally it performs a microwave expansion step, wherein the graphene is obtained by the urea nitrate intercalated graphite at a predetermined temperature by microwave heating, and is pulverized by a pulverizer to obtain a graphene sheet.