Waste rice straw was converted into activated carbon-supported manganese oxides (MnOx/RSAC) that were first used as a catalyst to improve the performance of ozonation of real paper-making wastewater. The results indicated that catalytic ozonation with the prepared catalyst exhibited a highly efficient performance in advanced treatment of paper-making wastewater, and the corresponding color and COD removal efficiencies were 58.5 and 77.5%, respectively. And the treated wastewater was more biodegradable and less toxic than that in ozone alone. Based on significant inhibition of the radical scavenger and fluorescence test in the catalytic ozonation process, we deduced that the enhancement of catalytic activity was responsible for MnOx/RSAC catalyzing ozone to generate more hydroxyl radicals and the possible reaction pathway was proposed. Thus, MnOx/RSAC catalyzing ozonation could serve as a stable, efficient, and economical process with a potential engineering application for treated refractory wastewater, and the results offered new insights for sustainable use of waste rice straw.