The effect of the partial pressure of CO and H2O on the initial reaction rate of LT-WGS over a Pt-Re/ZrO2 catalyst with Superior catalytic activity was evaluated. As a result, the reaction order was approximately zero with respect to CO and ca. 0.6 with respect to H2O, which indicates that CO is strongly adsorbed onto the catalyst surface in contrast to H2O. The theoretical rate equation was derived from the Langmuir-Hinshelwood (L-H) mechanism and was in good agreement with the experimental data.