The effects of impurities ions Al3+，Fe3+，F-，Mg2+ and SO42 - on the crystallization yield of urea phosphate(UP),its crystallization period, product size and crystal morphology were studied by means of batch crystallization process.The results showed that the dopant of Al3+,Fe3+ had siginificate effect on UP crystallization process,and without the crystal seed added in the reaction system, no crystals appeared when the system was cooled to normal temperature.On the conditions of 1% crystal seed added,with the increase of Al3+,Fe3+ mass fraction, the yield of UP gradually decreased,the crystallization period significantly prolonged, the product size was obviously reduced and the crystal morphology become irregular.Moreover, the aggregation degree was higher. The effect of Al3+ was somewhat larger than that of Fe3+ on above many aspects. With the increase of F- mass fraction，the yield of UP gradually decreased，the crystallization period did not change significantly，the product size decreased firstly and then increased slowly because of the embedding of the particle with each other and the crystal morphology become irregular.The impurity ions Mg2+and SO42 - had very little influence on the UP crystallization process,and the crystal morphology is regular and still is prism,the particles are in high dispersion state.