Water gas shift reaction in the presence of heterogeneous catalysts such as Ru/C, Pd/LaCoO3 and Fe3O4 was examined in supercritical water at 673 K from 0.1 to 0.5 cm(3) of water densities. These catalysts catalyzed water gas shift reaction and the main products were CO2 and H-2 center dot CH4 was formed from CO and H-2 produced by water gas shift reaction in the presence of Ru/C. CO conversion tended to decrease with increasing water density for all catalysts, which means that water essentially suppressed heterogeneous catalytic water gas shift reaction in supercritical water. The kinetics of water gas shift reaction was analyzed with an elementary-like reaction model using fugacity. The model calculation represented the trend of experimental results and revealed that the suppression of water gas shift reaction in high water density region was probably because water would cover on active sites and stabilize the adsorbed species on catalyst to decrease the ratio of vacancy of active sites on catalyst. (C) 2014 Elsevier B.V. All rights reserved.