Abstract: Flake graphite was used as raw material to make expandable oxidized graphite by intercalation oxidation, then the expanded graphite was obtained when expandable oxidized graphite was pyrolyzed at high temperature, and the graphene nanoplatelet was obtained by ultrasonic stripping of expanded graphite.FTIR, XRD, SEM, TEM and Raman were adopted to characterize the graphene nanoplatelet.The results indicated that expanded graphite with the largest expansion volume could be achieved with the expandable oxidized graphite being pyrolyzed at 800 ℃ for 30 s.The maximum volums of the expanded graphites from the 80 and 100 mesh flake graphites were 215 mL/g and 85 mL/g, and when they were ultrasonic stripped at 50 ℃ for 5 hrs, graphene nanoplatelets of 30 ~ 50 layers and 6 ~ 20 layers could be gained, respectively.