Abstract: Chloritization is a type of hydrothermal alteration widely developed in the Huangsha uranium deposit in the middle part of the Nanling Mountains. Based on petrographic studies, the authors investigated the types and morphological characteristics of chlorite minerals in No. 221 and No. 223 uranium deposits by using electron microprobe analysis, and classified chemical types of chlorite. Four kinds of chlorite production status were recognized, and the temperature and environment of the formation of chlorite as well as the relationship between chlorite formation and uranium mineralization was discussed. The results are as follows:(1) The early chlorite was mainly of biotite pseudomorph or starlike shape characterized by mass output, and the metallogenic chlorite was mainly produced in the vein. (2) There are four types of genesis i.e., chlorite biotite alteration, feldspar alteration, fracture filling type and uranium deposit association. (3) The chlorite-forming temperature was 200-310℃, and the average formation temperature of chlorite coexisting with uranium minerals was 215℃, suggesting a middle-low temperature hydrothermal deposit. (4) Chlorite was mainly formed in a reductive environment, and the formation mechanism was dissolution-precipitation and dissolutionmigration-precipitation.