The invention discloses a method for processing wastewater. The wastewater is high-acid heavy crude oil processing wastewater. The method comprises the following step: the high-acid heavy crude oil processing wastewater is successively contacted with an assistant catalyst A, an ozone catalytic oxidation catalyst and an assistant catalyst B, wherein the ozone catalytic oxidation catalyst contains a carrier and active components and auxiliaries which are loaded on the carrier. The carrier contains gamma-alumina. The active component elements contain Fe, Mn, Cu and Co. The auxiliary elements contain Ce and Mg. By the method for processing wastewater, physical and chemical performance stability of the ozone catalytic oxidation catalyst can be maintained for a long time, and COD cr value of wastewater is remarkably reduced. In addition, by the above method, the ozone catalytic oxidation catalyst used has long service life and high catalytic activity.