A　simple,　one-dimension　numerical　simulation　approach　is　presented　to　evaluate　Director　Methanol　Fuel　Cells　(DMFCs).　The　model　is　applied　to　simulate　the　cathode　phase　change　threshold　current　density　of　a　DMFC.　Considering　the　water　generation　rate,　water　transport　process　and　condensation　of　the　fuel　cell　air　cathode,　a　threshold　current　density　can　be　identified.　The　simulative　results　reveal　that　when　the　air　velocity　at　he　cathode　inlet　is　increased,　the　threshold　current　density　is　increased　too;　when　the　relative　humidity　of　gas　at　the　inlet　is　increased,　the　threshold　current　density　is　linearly　decreased;　longer　cathode　length　and　lower　operating　temperature　correspond　with　lower　threshold　current　density.