In view of the problems of uneven particle size and easy caking of ammonium persulfate crystalli zation products obtained in the actual production process, the thermodynamic test of ammonium persulfate was completed by combining theory and experiment; by analyzing the morphology, hygroscopicity and storage of ammonium persulfate crystalli zation products prepared by different processes, the internal and external causes affecting the caking were found, and the key control parameters and principles for reducing caking were determined; by optimizing the crystallization process of ammonium persulfate, the ammonium persulfate products with complete crystal pattern and meeting the quality standard were produced.