A water purification reactor using direct contact of gas corona discharge with water is developed into a cylindrical-anode wetted-wall reactor. In a modification from the previous plate anode to the present cylindrical anode, it is expected that reactive radicals produced in a plasma region around a wire cathode in a gas phase can efficiently reach the surface of a flowing-water film so that reactive species such as an OH radical can be effectively produced in water. In this study, aqueous phenol was decomposed using the modified reactor to evaluate its efficiency. As a result, the electron efficiency and energetic efficiency of the cylindrical-anode wetted-wall reactor were respectively 2-3 and 3-4 times greater than those of the plate-anode reactors. Furthermore, the activity of the radical-producing plasma in the proposed reactor was 2 orders of magnitude higher than that of the plate-anode reactor. The experiments applying varied water flow rates and discharge currents indicated that the condition that keeps a smooth water surface is important to achieve maximum decomposition efficiency. In addition, it is found that there is an optimized anode radius to attain high decomposition efficiency.