The invention discloses a method for purifying electrolysis primary liquid to remove cobalt in the process of purification, electrolysis and smelting of zinc, which comprises the following steps: under the action of ultrasound wave, adding permonosulfuric acid in zinc electrolysis primary liquid; and adjusting the pH value obtained in the step one by using zinc ore concentrate or zinc powder, oxidizing Co(II) in the solution into Co(III) at the temperature of 40-90DEG C and precipitation in the form of Co(OH)3. The invention has simple process and easy operation; by using the permonosulfuric acid as an oxidant, an oxidation potential higher than 2.3V can be provided and the degradation and reaction process can be strengthened; and by using power ultrasound as a synergic means, hydroxyl free groups can be generated in the reaction process, the oxidation potential can be further improved, the hydrolysis and precipitation process of cobalt can be strengthened and the aggregation of precipitation grains grow up. The invention cannot bring other impurities influencing the electrolysis process while efficiently purifying to remove the cobalt.