Abstract: The effects of pH value and cooling rate，Fe↑3+ and F↑- impurities on crystallization of potassium dihydrogen phosphate (KDP) were studied by the batch crystallization experiments.Results showed that： when the pH value was 3.0，the precipitation of crystals and crystallization temperature were both the highest.With the increase of pH value，the particle aggregation was obvious and the apparent size of crystals increased.With the increase of cooling rate，the metastable zone width and crystallization rate gradually increased，the average size of the crystals evidently reduced and the crystal nucleation rate was 4.The Fe↑3+ impurity had significant effect on crystallization process：the morphology changed from prism to spiculate，with the increase of Fe↑3+ impurity，and the crystal slenderness ratio，crystallization inducement time and the metastable zone width increased obviously as well.The impurity of F↑- had little effect on crystallization.With the increase of F↑- impurity，the slenderness ratio decreased，the metastable zone width increased slowly，but the crystal shape was changed from long prism to tetragonal prism and turned to podgy prism finally.The slenderness ratio decreased more in the presence of F↑- than just doping Fe↑3+ into the solution，but the effect of improving the crystallization was not up to much.Nevertheless，the experiment results have significance to direct the production of KDP.