Provided is a method for reducing COD of wastewater with improved utilization efficiency of ozone. The method achieves an objective by adding agents for removing hydroxyl radical scavengers produced by base-catalyzed ozone advanced oxidation to wastewater. The addition of calcium ion, barium ion, etc. to a base-catalyzed ozonation system makes the hydroxyl radical scavengers form precipitates, separated from water and lose the capability of scavenging hydroxyl radicals, thereby enhancing ozone utilization efficiency. Furthermore, calcium ion, barium ion, etc. form precipitates with partial organic acids yielded in the wastewater ozonation and are separated from water, hence diminishing ozone consumption and indirectly improving the ozone utilization efficiency in the wastewater treatment. The present invention can not only significantly enhance the reaction rate and utilization efficiency of ozone, saving reaction time and costs, but also enable complete mineralization of the organic compounds, significantly reducing COD and total phosphorus of wastewater.