Due　to　the　increased　popularity　of　hydrogen-based　electricity　generation　technology,　unitized　regenerative　fuel　cells　can　be　regarded　as　an　electricity　conversion　device　coupling　two-phase　behaviors.　Water　management　inside　the　cell　is　important　to　complete　a　suitable　start-up　characteristic　of　unitized　regenerative　fuel　cells　when　changing　the　working　modes.　In　this　study,　investigations　on　fundamental　of　water　expelling　principles　and　influence　of　residual　liquid　water　on　cell　behavior　are　performed　numerically　utilizing　a　three-dimensional　two-phase　model.　The　model　involves　in　charge,　gaseous　species,　liquid　water,　dissolved　water　and　heat　transfer.　Experiments　are　conducted　to　validate　reaction　modes　through　voltage-current　density　curves.　Dynamic　responses　of　water　in　various　phases　(liquid　and　dissolved　phase)　are　obtained　in　a　purging　mode,　which　is　initiated　by　an　electrolytic　cell　mode.　Gas　purging　procedure　has　various　of　impacts　on　the　performance　under　different　purging　time　conditions.　Under　the　same　purging　result　condition,　operational　voltage　exhibits　significant　influence　on　cell　performance　at　the　start-up　stage.　The　relative　humidity　has　an　important　influence　on　output　performance.　Those　results　originate　from　the　complex　effects　of　the　residual　water　in　a　purging　mode,　as　well　as　the　liquid　water　condensed　in　during　the　fuel　cell　operation　procedure.