A　new　two-dimensional,　two-phase　flow　model　based　on　the　mixture　flow　model　was　developed　to　investigate　the　water　transport　and　distribution　in　the　proton　exchange　membrane　(PEM)　fuel　cell.　The　model　couples　the　flows,　species,　electrical　potential,　and　current　density　distributions　in　the　cathode　and　anode　fluid　channels,　gas　diffusers,　catalyst　layers,　and　membrane,　respectively.　The　catalyst　layers　are　now　included　in　the　respective　unified　domains　for　the　cathode　and　anode.　Furthermore,　the　two-phase　flow　model　was　also　used　in　the　anode　side,　and　the　momentum　transfer　between　the　liquid　and　gas　phases　due　to　phase　change　was　taken　into　consideration.　The　model　was　used　to　study　water　transport　and　its　distribution　in　the　cathode,　the　anode,　and　the　membrane　of　PEM　fuel　cell　simulation　results　show　that　the　increase　of　humidification　temperature　and　current　density,　or　the　decrease　of　fuel　cell　temperature　makes　the　increase　of　water　content　in　membrane,　leading　to　the　increase　of　ionic　conductivity　and　overpotential　of　concentration　difference　in　cathode　attributed　to　flooding.