<p>We have investigated the degradation characteristics of ultra-high molecular weight polyethylene in decalin, and determined the rate constant and activation energy of degradation. We found that oxidative degradation of UHMWPE is more easily achieved than thermal degradation, and oxidative degradation occurs mainly in high oxygen atmosphere. Since the degradation is a reaction with changing molecular weight rather than concentration, we considered the reaction rate with respect to molecular weight. In addition, the kinetic equation with respect to molecular weight conversion was considered to determine the reaction rate constant irrespective of the reaction order, as the order of the reaction increases with temperature, and the reaction rate and Arrhenius constant were determined. In addition, as the order of the reaction increases with temperature, the kinetic equation with respect to molecular weight change rate was considered to determine the reaction rate constant irrespective of the reaction order, the reaction rate and Arrhenius factor were determined.</p>