Abstract: There are a large number of anions and cations in the production of wet process phosphoric acid by DH process，which is difficult to remove out in the process of phosphoric acid purification.When synthesis of urea phosphate with the wet process phosphoric acid directly，these impurity ions affect the metastable zone width，and therefore affect the product yield and quality. Test by changing the ratio of raw materials，reaction time，reaction temperature，cooling rate，crystallization temperature，and stirring speed etc. to explore the optimum conditions for the production of urea phosphate.The influences of several main impurities， such as SO42-，SiF62-，Fe3+，Al3+，and Mg2+ in the phosphoric acid by wet process on the yield and quality of urea phosphate product were analyzed.In the experiments it was found that a certain amount of SiF62- concentration will help to improve production yield，but its concentration should not be too high. SO42-，Fe3+，Al3+，and Mg2+ will reduce the production yield of urea phosphate，especially，Fe3+ and Al3+ had a greater impact on the production yield.

Key words: phosphate, urea, urea phosphate, crystallization, impurities