The whole process of the thermal decomposition of GAP was investigated by thermolysis-MS,TG-DTG-FTIR,in-situ thermolysis-FTIR coupling techniques,and possible mechanisms of GAP′s thermal decomposition is proposed. It has been proved that the major decomposition products in the gas phase include N₂,NH₃,HCHO,HCN,H₂CCO etc. In the condensed phase,the formation of some aromatic intermediates was observed,and when temperature raised to 450 ℃,the characteristic absorbances of aromatics disappeared and a black-brown residue was formed.