Kinetic models of pyrolysis and oxidation reactions of cationic ion-exchange resins were investigated in this study. Activation energy and reaction model for each of different reaction steps were established by the analysis of non-isothermal TGA data by applying an isoconversional method and a master-plot method. Primary thermal dissociation of SO3H+ from divinylbenzene copolymer at 200-400°C was well described by a phase boundary controlled reaction (contracting volume, 3(1-a)2/3) and its average activation energy was determined to be 143.58 kJ/mole. Pyrolysis reaction of remaining divinylbenzene copolymer at higher temperature of 400-1400°C was also described by the same model, but average activation energy was relatively much small as 65. 24 kJ/mole. The oxidation of divinylbenzene copolymer at 400-800°C in the presence of oxygen was well described by a different phase boundary controlled reaction (contracting area, f(a)=2(1-a)0.5) and its average activation energy was determined to be 111.52 kJ/mole.