Supercritical solvent is used as a reaction mediumin which the solvent either actively participates in the reaction or functions solely as the solvent medium for the reactants, catalysts and products. A mathematical model has been developed and tested with experimentalt data formethanol oxidation in supercriticalwater. The model is based on a material balance in a differential element of reactor and is subjected to constant temperature and presser through the reactor length. In this work, rung- kutta of forth order is used to solve the differential equations and obtain the concentration profiles through the reactor length. The agreement between calculated concentrations and methanol conversion with experimental data confirms the validity of the developed model. Once the validity of the model is checked , the effects of variables such as the residence time, temperature and feed ratio upon the conversion of methanol are surveyed.