Abstract: Few research has been carried out on the influence rules and mechanism of graphite scale size on expanded volume. In this paper, different scale graphite was selected and expanded under the same process conditions. The structure and morphology of graphite concentrate, interlayer compound and expanded graphite were characterized by XRD and SEM, and the reaction kinetics model and expanded graphite packing model were established. The results showed that the larger the graphite scale, the higher the expanded volume of expanded graphite. Microscopically, pyrolysis of graphite intercalation compounds produces a gas that acts on large scale flake graphite for a long time, resulting in a large interlayer spacing; Macroscopically, the expanded volume is different due to different packing methods of expanded graphite.