Abstract: A series of melamine phytates/rigid polyurethane foam (MEL-PA/RPUF) composites were prepared by one-step water-blown method with MEL-PA as flame retardant. Thermogravimetric analysis (TG) and thermal analysis kinetics were used to study the thermal stability of the composites and reveal its degradation mechanism. The results show that the char residues of MEL-PA/RPUF gradually increases at 700℃ with the increase of MEL-PA loading. Based on TGA data, the reaction grade n, activation energy E and pre exponential factor A of the main degradation stage for the composites were calculated by the Coats-Redfern and Horowitz-Metzger integration methods. The results show that MEL-PA promotes the initial degradation of the composites in air atmosphere, while the MEL-PA/RPUF composites have higher thermal stability in the high temperature stage, and the two calculation methods have the same law. In N₂ atmosphere, MEL-PA30/RPUF (mass fraction of MEL-PA is 10.3wt%) has higher n and E compared with RPUF. The results indicate that the reaction of MEL-PA30/RPUF is more complex and the thermal stability is higher. The mathematical model and experimental analysis by Criado method verify the feasibility of the Coats-Redfern method. The results of thermal degradation kinetics of MEL-PA/RPUF composites provide reference for the analysis of flame retardation performance of RPUF with different flame retardation systems.