Abstract: Anion SO42- in orthophosphoric acid  was removed by cooling crystallization method with the 98%（H3PO4，mass fraction） orthophosphoric acid got from the purification and concentration of industrial grade wet-process phosphoric acid as raw material.The influences of cooling rate，stirring speed，crystal growth substance dosage，and crystal maturing time on the removal effect were investigated.The optimum technological conditions were comfirmed as follows：the stirring speed was 300 r/min，the cooling rate was 1 ℃ per 15 min，the growth substance dosage was 5 g，and the crystal maturing was 1.5 h.Under the best process conditions，SO42- of orthophosphoric acid removal rate reached 82.1%，mass fraction of  SO42- less than 20 mg/kg， meeting the 85% quality requirement for SO42- of food grade phosphoric acid，and improved the added-value of products.At the same time，this method provided a feasible way for the production of orthophosphoric acid with low content of SO42-.

Key words: orthophosphoric acid；SO42-；crystallization, removal