The invention belongs to the technical field of titanium dioxide powder and particularly relates to a method for treating sulfuric-acid-process titanium dioxide spent acid. The method for treating thesulfuric-acid-process titanium dioxide spent acid, disclosed by the invention, comprises the following steps: a two-step method: (1) mixing anhydrous sulfate with the spent acid, carrying out standing, and carrying out solid-liquid separation so as to obtain a solution, wherein the mass concentration of sulfuric acid in the solution is 35% to 38%; and (2) mixing the anhydrous sulfate with the solution obtained in the step (1), carrying out standing, and carrying out solid-liquid separation so as to obtain a solution, wherein the mass concentration of the sulfuric acid in the solution is 60% to 70%; a one-step method: mixing the anhydrous sulfate with the spent acid, carrying out standing, and carrying out solid-liquid separation so as to obtain a solution, wherein the mass concentration of the sulfuric acid in the solution is 60% to 70%; and the anhydrous sulfate is one of anhydrous cobaltous sulfate, anhydrous nickel sulfate and anhydrous cadmium sulfate. According to the spent acidtreatment method provided by the invention, waste raw materials resulting from titanium dioxide production are effectively utilized, and pressure caused to environments can be further alleviated, so that the method has an extreme industrial application prospect.