Abstract: A novel non halogen intumescent flame retardant polyamide 66 was proposed, in which ammonium polyphosphate(APP,acid source) and nylon 66(polymeric matrix, gas source and carbonific agent) were involved. The thermal degradation and flame retardant process of IFR system have been studied by TGA. Based on kinetic data(activation energy E ), it shows that the thermal degradation process of polymer PA 66 was dramatically held earlier due to the presence of APP rendering its flame retardance much improved.