Expandable graphite (EG), a kind of environmentally friendly flame retardant, expands when heated, forming a loose and porous structure, which can effectively insulate the polymer from oxygen and heat sources. However, the compatibility between EG and polymer is poor, which will greatly reduce the mechanical property of the materials. In this paper, the modification methods of EG and its research progress in flame retardant polymer materials are reviewed from the aspects of surface coupling treatment, blending synergy and hybrid modification. Meanwhile, the advantages and disadvantages of different approaches are also discussed, and future research on EG flame retardant polymers is also prospected.