Treatment of toxic organic compounds is one of the major applications of the Wet Air Oxidation (WAO) processes. The process can be defined  as the oxidation of substances, either in the form of solutions or suspensions, with the use of an oxidant (oxygen or air) at elevated pressure and temperature. The aim of this paper was to study of Catalytic Wet Oxidation (CWAO) with hydrogen peroxide to improve removal efficiency of organic matter and ammonia mainly produced in Isfahan composting factory leachate. The experiment was carried out by adding 1.5 Lit pretreated leachate sample to 3 Lit autoclave reactor. Four parameters are considered: pressure (8–12 bar); temperature (100–300 °C); retention time (30–90 min); H2O2 (1–5 mL/L).The highest removal efficiencies of COD and BOD were achieved at 300°C; approximately 44% and 48% were destroyed, respectively. On the other hand, highest ammonium removal efficiency was achieved at 100 °C in which approximately 63.8% was removed. The efficiency of aqueous phase oxidation can be largely improved by the use of H2O2 as catalyst. Therefore, catalytic wet oxidation would provide an environmentally attractive option for control of organic and toxic wastes problems. Temperature was found to be the most important control variable of the wet oxidation process of leachate.