Abstract: Intermittent cooling-crystallization method was employed to find out the influences of contents of typical anionic impurities，such as SO₄^2-，F^-，Cl^-  in the wet process phosphoric acid，the raw material of sodium dihydrogen phosphate，on the crystallization process of sodium dihydrogen phosphate.Induction period，crystallization rate，particle size distribution，and slenderness ratio are applied to characterize crystal nucleation，crystal growth，and crystal morphology，respectively.Experimental results indicate that with the increase of SO₄^2- content，the induction period and the average particle size decrease，whereas the crystallization rate increases firstly，and decreases afterwards；with the increase of F-content，the induction period，crystallization rate and average particle size all increase gradually；with the increase of Cl^- content，induction period decreases， crystallization rate increases，and average particle size increases at first，and then decreases.These research results can be used to guide the industrial production of sodium dihydrogen phosphate from wet process phosphoric acid.

Key words: sodium dihydrogen phosphate, anionic impurities, induction period, particle size distribution