The　electrolyzing　and　fuel　cell　(FC)　modes　appear　in　a　unitized　regenerative　FC.　Understanding　the　operating　condition　impacts　on　the　dynamic　behaviors　during　mode-switching　procedure　facilitates　better　handling　of　cell　working　states　and　increasing　the　performance　behaviors.　In　the　present　paper,　a　two-dimensional　transient　numerical　model　is　employed　to　discuss　the　influence　of　operating　conditions　on　two-phase　species　distributions　when　switching　the　cell　mode　into　FC.　According　to　the　numerical　results,　it　is　concluded　that　when　the　cell　switches　from　electrolytic　cell　to　the　mode　of　FC,　reducing　the　operating　cell　voltage　can　significantly　improve　the　cell　performance.　At　the　same　time,　concentration　polarization　and　temperature　heterogeneity　are　serious.　Increasing　the　gas　inlet　velocity　can　improve　the　cell　performance.　Providing　the　reaction　gas　with　the　same　concentration　as　the　FC　mode　in　advance　can　improve　the　temperature　uniformity　and　cell　current　density　values　when　starting　switching　the　mode　but　hardly　impacts　the　parameter　value　and　currents　after　stabilization.