This halogen-free, mineral based flame retardant is made of modified expandable graphite which can be used in polyurethane hard foam/soft foam, polyethylene, polypropylene, resin, coating and other plastics. Expandable graphite flame retardant combines two modes of action in one additive: the flammability of the component is reduced on the one hand and, on the other hand,graphite forms a protective expanded layer in case of a fire. A large number of tiny holes are formed, which can absorb the smoke generated in the combustion process. With graphite flame retardant, cold room PU can reach B1 degree with oxygen index improved by 4-10 without destroying PUs physical properties. Hydrophobic suspension and excellent flame retardant effect, good compatibility with organic system, which can solve the problem of water absorption of flame retardant. When the amount of modified graphite is 20-35 phr / 100 phr, the oxygen index can be increased by 6-10.