At present, it is urgent to synthesize highly active ozone decomposition catalysts to cope with the ever-increasing ozone concentration in the atmosphere. In this study, a highly porous Cu₂O catalyst was prepared by using combined surfactants of triblock copolymer P123 and n-butanol through a simple solution reduction method by ascorbic acid. Transmittance electron microscopy, X-ray diffraction, and N₂ adsorption–desorption characterizations verify the highly porous structure with a relatively high surface area of 79.5 m²·g⁻¹ and a small crystallite size of 2.7 nm. The highly porous Cu₂O shows 90% ozone conversion activity in harsh conditions, such as a high space velocity of 980,000 cm³·g⁻¹·h⁻¹, or a high relative humidity of 90% etc., which is not only attributable to the high surface area but also to the high concentration of surface oxygen vacancy. The results show the promising prospect of the easily synthesized, highly porous Cu₂O for effective ozone decomposition applications.