The flame retardancy of triazine charring agent terminated with butylamine (charring agent-2) in polypropylene (PP) was studied by limiting oxygen index (LOI) measurement, vertical burning test and cone calorimetry test, with non-terminated charring agent (Charring agent-1) as comparison. It is shown that the intumescent flame retardants (IFR-1 and IFR-2), which respectively is composed of charring agent-1, charring agent-2 and ammonium polyphosphate (APP), have good flame retardancy in PP. The flame retardancy of IFR-1 and IFR-2 has no significant difference from the results of the vertical burning test and LOI, while the flame retardance of IFR-2 is better than that of IFR-1 from the results of the cone calorimetry test. It is shown from the analysis of the residue obtained in CCT that polymetaphosphoric acid from the decompostion of APP in the process of combustion promotes the dehydrateion and carbonization of charring agent, and the char is changed into the intumescent layer by the foaming of inert gases released from the decomposition of APP, charring agent and PP. The flame retardant effect is consequently resulted from the intumescent layer through heat and oxygen insulation, prevention of pyrolysis volatilization as well. The chlorine content of charring agent is effectively reduced and the thermal stability is markedly improved when the charring agent is terminated with butylamine, which makes it meet the halogen-free requirements of flame-retarded products better, is in favor of improving the environment of plastic processing, and prevents the corrosion of processing equipments.