Abstract: Expanded graphite (EG)-reinforced epoxy composites were prepared by a solution mixing method. The structure and morphology of the EG/epoxy composites were investigated by XRD, FE-SEM and HR-TEM. The EG prepared by acid oxidation and thermal expansion shows good compatibility with the epoxy resin that enters the EG layers to decrease their thickness to 60-70 nm, owing to its abundant oxygen-containing functional groups. With the addition of 9 wt% EG, the thermal decomposition temperature of the composite increases from 340 to 480℃, the electrical conductivity from 10-15 to 10-5 S/cm and the tensile stress is increased by more than 30%. These improvements are attributed to the good dispersion of EG sheets in the epoxy matrix.