Tributhyl phosphate (TBP) decomposition in supercritical water oxidation (SCWO) was performed with and without catalyst, at different temperatures ranging from 370 to 480 degrees C, and different reaction times. Ag2O, CuO, Fe2O3, MgO, and ZnO synthesized by supercritical water were examined in TBP decomposition as the catalyst. TBP structure decomposed under the non-catalytic reaction; nevertheless, the results indicated that the use of catalysts improved the reaction efficiency, which calculated based on total organic carbon (TOC) removal, by far. However, TOC removal using Fe2O3 was 20% higher than the non-catalytic reaction. Having the ability in completion of the redox cycle, iron oxide catalytic nanoparticles preserve their stability and performance when used in a sequential TBP decomposition experiment. As for the estimation of the reaction rates, the kinetic constants were evaluated. Possessing a high predictive power with the accuracy more than 90%, the proposed kinetic equations can be applicable for further studies dealing with the TBP decomposition adopting SCWO.