In order to solve the problem of caking in the storage process of 66% water-soluble monoammonium phosphate of an enterprise in Yunnan,the research idea of adding anti-caking agent into monoammonium phosphate concentrated clear li-quid to achieve anti-caking effect was put forward.Combining with the rapid determination method of caking performance,laboratory research and development were carried out,and the anti-caking agent with the best anti caking effect was obtained,which was verified by industrial test.The test results showed that adding 0.05% anti-caking agent octadecylamine into monoammonium phosphate concentrated clear liquid could effectively improve the caking problem of 66% water-soluble monoammonium phosphate,and the addition of anti-caking agent had no impact on the product quality;the products obtained in industrial test could meet the industry standard HG/T 5048—2016 quality requirements of type Ⅱ in water soluble monoammonium phosphate.