In the present study, 12 kinds of metal oxides (V2O5, Cr2O3, MnO2, Fe2O3, Co2O3, CuO, ZnO, ZrO2, MoO3, SnO2, WO3 and CeO2) were tested in supercritical water gasification of glucose at 600 °C. Quartz capillary reactor was used to eliminate the potential catalytic effect of the reactor wall. The influence of metal oxides on the gasification efficiency, gas composition and yield was studied. Most metal oxides improved the gasification efficiency, and Cr2O3, CuO, WO3 and V2O5 were the most effective ones. Most oxides had little influence on H2 fraction but showed significant influence on CO fraction. The lowest CO fraction was achieved with MnO2 and CuO. The catalytic activity of the metal oxides was summarized and compared based on their impacts on the gas composition and yield. Through the visualization of the reactor, CuO was found to be reduced into Cu metal during gasification. Both the presence of Cu metal and released oxygen were supposed to enhance the gasification. Further study on the valence state of metal oxides after gasification may help to reveal the catalytic mechanism of the metal oxides.