Abstract: By using in-situ and on-line Fourier transform infrared spectroscopic methods (FTIR),the dynamic change of solid and gaseous products of acrylonitrile (AN) /diacetone acrylamide (DAA)/methylacrylate(MA) copolymers was monitored durin g its pyrolysis innitrogen atmosphere. It was found that at lower temperature of pyrolysis (below 300℃) the cyclization,occurred mainly, then the dehydrogenation reactions. The samples were eventually pyrolyzed at the temperature between 300℃ and 950℃. The gaseous products evolved were HCN, NH₃, CH₄, CO₂, CO etc. and the solid residues were of amorphous carbonaceous structure.