An empirical model is proposed for the decomposition process of phenol in water by direct contact of gas corona discharge in a cylindrical wetted-wall reactor. The proposed model is based on an assumption that reactive radicals in water, OH, induced by the corona discharge are the main species to decompose phenol and its derivatives. The phenol degradation characteristics calculated by this model are successfully correlated with the experimental data obtained with many varied parameters, such as the discharge current, diameter of the wire cathode, axial length of the discharge zone, radius of the cylindrical anode, and water flow rate. The calculated results can also show the effect of the ion wind. The proposed model will be useful to the design of water purification systems using the relevant method, which has lately been developed as an effective technique to decompose stable organic compounds.