Supercritical water oxidation (SCWO) was carried out in a flow-type reactor for modeling of wastewater containing phthalic or adipic acid. For each acid, the reaction order and rate constant, k, were determined over a wide range of experimental conditions : temperatures from 633.15 to 713.15 K, pressures from 18 to 29 MPa, excess amounts of hydrogen peroxide from zero to 800 percent, and the mean residence time in the reactor from 1.1 to 49.1 seconds. The concentration of both acids in model wastewater was set by 500 ppm. For phthalic acid, we found that the orders of decomposition reaction with respect to the reactant concentrations were 0.56 for phthalic acid, 0.31 for hydrogen peroxide, and 0.53 for water. For adipic acid, the orders of oxidation were 0.78 for adipic acid, 0.53 for hydrogen peroxide, and 0.74 for water. Then measured activation energy for phthalic acid was 33.08 kcal/mol and that for adipic acid was 19.51 kcal/mol, respectively.