Polypropylene (PP) has the disadvantage of flammability and easy dripping, flame retardant was incorporated into polymer to improve the thermal and flame retardant property. Conventional flame retardant containing halogen would release toxic gases when the materials got fire and let the people died in the fire and destroy the environment. Intumenscent flame retardant consists of three key components: acid source, carbon source and blowing agent. Acid source is phosphoric acid, which can dehydrate the materials. Carbon source can form char layer to prevent further thermal degradation. The blowing agent can swell the carbon layer to avoid heat and mass transfer during material get fire. Novel intumenscent flame retardant which contains phosphorus and nitrogen was successfully prepared. FTIR, TGA, LOI and UL-94 were used to characterize the structure, flame retardant mechanism and thermal property of the composites. LOI and UL-94 data showed the composites possess excellent flame retardant property. For kinetic of thermal degradation.