Performance stability of the direct dimethyl-ether fuel cell is first studied in this report. The polymer electrolyte fuel cells of Pt-Ru (anode)/Nafion117 (electrolyte)/Pt (cathode) are used. The cell voltage change of the cells are examined under constant load of 0.288A/(cm)^2 at 120℃ and 0.45MPa. Intermittent pulsing voltage falls and continuous voltage falls are observed. They are not improved by increasing anode steam from 107%RH to 139%RH. By increasing anode catalyst from 1.0mg/(cm)^2 to 4.0mg/(cm)^2,the cell voltage become stable while the intermittent pulsing voltage falls are not observed. However, when the time passed, the cell voltage remains unstable while the intermittent pulsing voltage falls are observed.
