The exfoliated graphite (EG) was prepared by the microwave treatment for graphite-SO₃ intercalation compounds (GIC). GIC was prepared by direct reaction of flake graphite with SO₃ gas. The maximum amount of loaded SO₃ per 1 g of graphite is over 0.6 g, depending upon reaction time and SO₃ concentration. The XRD pattern for the GIC shows that the (002) reflection of graphite (d=0.335 nm) disappears and the patterns change with reaction time. The bulk density was a range of 4.5 × 10^-3 g/cm³ to 9.5 × 10^-3 g/cm³, depending on the reaction time with SO₃ gas. The oil sorption capacity for exfoliated graphite with 5.1 × 10_-3 g/cm₃ of bulk density by microwave treatment was found to be 88 g of c-grade heavy oil, 75 g of crude heavy oil, and 55 g of diesel oil per 1 g of exfoliated graphite. This result indicates that the volume expansion by microwave can be another route for the preparation of exfoliated graphite with excellent physical properties.