The invention relates to a method for recovering phosphoric acid by electrolyzing a mixed acid solution, belonging to the field of resource recovery. The method comprises the following steps: puttingthe mixed acid solution into a product tank, wherein the mixed acid solution comprises phosphoric acid, oxyacid and organic acid; and inputting the mixed acid solution in the product tank into an electrolytic cell for cyclic electrolysis, reducing the oxyacid at the cathode of the electrolytic cell, oxidizing the organic acid at the anode of the electrolytic cell, and collecting gas generated in the cyclic electrolysis process through a gas collecting device so as to recover phosphoric acid in the mixed acid solution. The oxyacid is preferably nitric acid, nitrous acid, perchloric acid or hypochlorous acid, and the organic acid is preferably acetic acid, oxalic acid or propionic acid. According to the invention, phosphoric acid recovered through electrolysis can reach 99% or above, the technological process of treatment is simple, environmental pollution caused by direct discharge of waste acid liquid can be avoided, the additional value of products is high, and good economic benefitsand environmental benefits are achieved.