Abstract: In this study, the chlorination mechanism and influencing factors of uranium oxides(mainly U₃O₈)  were studied by using CCl₄ and HCl gas as chlorination reagents respectively. The chlorination of U₃O₈ powder was studied with CCl₄ as chlorination reagent. The mechanism and kinetic behavior of the chlorination reaction were studied by thermogravimetric analysis. The main chlorination product is UCl₄. The chlorination of different types and morphologies of uranium oxide by CCl₄ was also studied. The UO₂ pellets are difficult to chlorinate due to their very dense structure. UO₂ powder and UO₃ powder are easily chlorinated by CCl₄, and the chlorination products are UCl₄ and UCl₆ respectively. The chlorination of U₃O₈ powders in LiCl-KCl molten salt system was carried out using HCl gas as the chlorination reagent. The effects of reaction temperature, chlorination time, HCl gas flow rate, feeding amount of U₃O₈ powder, and uranium oxide types and morphologies were studied. The results show that increasing the reaction temperature, prolonging the reaction time, and increasing the HCl gas flow rate are beneficial to the improvement of the chlorination rate. The process parameters of HCl gas chlorinated U₃O₈ powder are recommended as follows: the chlorination reaction temperature is 500 ℃, and the flow rate of HCl gas is 0.6 L/min.