A kinetic analysis method for the degradation of polymer in supercriticai fluid was proposed in this work. The method was applied to predict the degradation of polystyrene (PS) in supercritical acetone by nonisothermal weight loss technique with heating rates of 3, 5, and 7 degrees C/min. To verify the effectiveness of the kinetic analysis method proposed in this work, the experimental values were compared with those of the numerical integration results using kinetic parameters obtained in this work. It was found that the kinetic analysis method proposed in this work gave a reliable value of kinetic parameter for PS degradation in supercritical acetone. The kinetic parameters were also compared with the values of thermal degradation of PS in the nitrogen atmosphere reported in the literature.