Abstract: In order to process highly tritiated water, a two-stage palladium membrane reactor with hydrogen-water isotope exchange series with water gas shift has been built, which can realize the cascade treatment process. In this paper, hydrogen removal experiments were carried out with natural water instead of tritiated water as the source and D₂ instead of H₂. The maximum decontamination factor(DF) of 207.4 is obtained, which verifies the feasibility of using two-stage palladium membrane reactor to treat tritiated water. In general, the DF of water gas shift reaction is greater than that of hydrogen-water isotope exchange reaction. The higher the ratio of D₂/H₂O in the hydrogen-water isotope exchange, the greater the DF. The higher the feed side pressure, the greater the DF. With the increase of feed water flow, the DF values of both reactions will decrease. Because hydrogen-water isotope exchange can reduce the concentration of tritiated water by more than one order of magnitude, the contact between CO and high concentration of tritium in the second membrane reactor can be avoided as far as possible, and the generation of tritium-containing organics can be inhibited. Thus it can be seen that the two-stage palladium membrane reactor is expected to be a highly efficient device for processing of tritiated water.