The invention belongs to the technical field of spent fuel postprocessing, and discloses a method for destructing oxalic acid in a plutonium oxalate sediment mother solution. The method comprises the following steps that a direct-current power source capable of achieving periodic reverse is utilized for electrolyzing the plutonium oxalate sediment mother solution under the constant-voltage condition, and platinum electrodes or titanium-plated platinum electrodes are adopted as a cathode and an anode, wherein the reverse period of the direct-current power source is the time spent when the anode is passivated, and the constant voltage is an electrolytic oxidation decomposition peak potential value of the oxalic acid in the plutonium oxalate sediment mother solution. The method has the beneficial effects of being capable of effectively avoiding anode passivation and anode oxidation, and being high in electrolytic efficiency and high in electrolysis speed.