The present invention provides a potentiometric titration method of calculating a content of each acid in a mixed acid solution. The potentiometric titration method includes steps as follows. Step 1, an alkali-alcohol solution of a concentration in 0.1˜0.2 mol/L is prepared and titrated with a basis reagent. Step 2, a first solvent and a second solvent are added into and stirred with a mixed acid solution consisted of nitric acid, phosphoric acid and acetic acid to form a mixed system, and the mixed system is titrated with the alkali-alcohol solution to obtain three equivalence points of the nitric acid, phosphoric acid and acetic acid in the mixed system. Step 3, a concentration of each acid in the mixed system is measured with the three equivalence points obtained in Step 2. According to the present invention, the content of each acid in the mixed acid solution can be rapidly and precisely measured.