Chloritization is one of the most important alteration types in the Longshoushan uranium deposit. Based on EPMA analysis and mineralogical study of the chlorites in the Longshoushan uranium deposit, the authors found that the chemical types of chlorite in Longshoushan area is mainly mafic chlorite, with a small amount of ripidolite. Based on the genesis or the relationship with coexisting minerals of chlorite, the authors divide the chlorites into four types, i.e., biotite alteration type, feldspar alteration type, pitchblende association type and accessory mineral association type. Argillaceous rock is the main protolith of chlorite, which is the product of multi-stage geological activities. Studies show that the uranium mineralization process of the Longshoushan alkali-metasomatic type uranium deposit experienced different temperatures at different stages: At first, the hydrothermal solution was of high temperature and resulted in the chloritization of biotite, and then the metasomatism of feldspar formed chlorite of feldspar alteration type. At the mineralization stage, the hydrothermal solution was of low temperature and formed chlorite closely associated with pitchblende. In the process of uranium mineralization, chlorite not only activated uranium in the granite but also offered a favorable deposition environment.