Abstract: Mineralogical and geochemical study of chlorites from the Xiangcaoping and Douzhashan granites in the Miaoershan area was carried out to analyze types and formation environments of chlorites and factors restricting uranium mineralization. Mineralogical characteristics reveal that the chlorites in granites of Xiangcaoping and Douzhashan were altered mainly from biotite. But alteration degree of the Douzhashan granite is stronger than that of Xiangcaoping granite. Geochemical characteristics indicate that the Douzhashan granite contains more ions(such as Al³⁺ and Fe²⁺)compared with the Xiangcaoping granite. Chlorites of the Xiangcaoping granite consist of ripidolite and brunsvigite, while chlorites of the Douzhashan granite of thuringite and ripidolite. Compared with the Xiangcaoping granite, the Douzhashan granite underwent strong chloritization with a high content of Fe²⁺. This illustrates that the Douzhashan granite was characteristic of higher reducing capacity than the Xiangcaoping granite, causing reduction of U⁶⁺ in the fluid into U⁴⁺, which much benefits for uranium mineralizing. This may be the reason why the Douzhashan granite can host uranium deposits wh2·1ile the Xiangcaoping granite can not.