Experimental and theoretical feasibility studies of a catalytic reduction method were carried out for application to the tritium recovery processes in fusion reactor systems. Experiments on the decomposition of water vapor were performed under the following conditions: temperatures of 350 to 650 K; an H2O vapor concentration of 103 to 104 ppm; a mole ratio of CO to H2O of 1 to 10; and a space velocity of 2 × 102 to 2 × 104 h−1. The catalyst used was a mixture of CuO, ZnO, and Cr2O3. It has been demonstrated that this method using the zinc-stabilized catalyst can be adapted to recover tritium from tritiated water with a high conversion ratio (>0.999 per one path) at comparatively low temperature (450 K). The catalytic rate equation and the rate constants determined by this work can be used for designing a practical catalytic reduction bed for the decomposition process of the tritiated water.