Polypropylene／clay nanocomposites were prepared with three monomers solid—phase grafted PP as compatibilizer The nanostructures were characterized by X—ray diffraction (XRD) and transmission electron microscopy(TEM)．Dynamic thennogravimetric analysis(TGA)of PP and the nanocomposites was petformed Flynn-Wall-Ozawa and Kissinger equations were used to compute the weight loss data and calculate the activation energias of decomposition．The temperature of weight loss of 10％ for the nanocomposites is 40 K higher than that for the neat PP．The decomposition region for the nanocomposites was also found to be much narrow than that for the neat PP．The apparent activation energy of thermal decomposition of the nanocomposites was 50％ higher than that of the neat PP.