采用一步投料法，将磷铵、尿素和硫酸镁充分混合后粉碎，再加入反应器中原位螯合制备含镁元素的水溶性聚磷酸铵（APP）肥料。研究镁添加量、尿素/磷铵物质的量比、反应温度、反应器搅拌转速对产品聚合度及聚合度分布的影响。结果表明：当镁添加量＜5%（质量分数）时，可以促进磷铵与尿素的聚合反应，提高产品聚合度；增加尿素比例、提高反应温度，可显著提高产品聚合度；随着反应器搅拌转速增加，含镁APP产品聚合度增加，而纯APP产品聚合度降低。各实验因素对APP聚合度的影响由大到小顺序为尿素/磷铵物质的量比、反应温度、搅拌转速、镁添加量。

Monoammonium phosphate（MAP），urea and magnesium sulfate were fully mixed and ground to feed into reactor for making ammonium polyphosphate（APP） which contained chelated magnesium by one step feeding method.The effect of magne sium content，urea/MAP amount of substance ratio，reaction temperature and stirring speed of reactor on the polymerization degree and distribution of polymerization degree of the products were investigated.Results showed that the polycondensation between MAP and urea was promoted when the magnesium content was less than 5%.The polymerization degree of APP was significantly increa sed by augmenting the urea proportion and increasing reaction temperature.With the increase of reactor stirring speed，the po lymerization degree of APP containing magnesium increased，while that of pure APP decreased.The order of various exper imen tal factors effecting on APP polymerization degree were the amount of substance ratio of urea/MAP>reaction temperature>stirring speed>magnesium content.