The kinetic characteristics and mechanism of potassium release in the molybdenum concentrate treatment process were studied by kinetic analysis and analytical techniques such as SEM-EDS, MLA and ICP. The results show that the first-order kinetic model is the best kinetic model of potassium release in the water washing and ammonia leaching process. Potassium is present in molybdenum concentrate in the form of soluble potassium ions and four potassium minerals. During the roasting process of molybdenum concentrate, some muscovite decomposed into orthoclase, while other muscovite combined with impurity metal elements to form anandite. Furthermore, the transformation of muscovite to orthoclase could be effectively inhibited by the rapid cooling of molybdenum calcine. The results could provide a basis for reducing potassium content in ammonium molybdate products.