This　paper　focuses　on　a　proton-exchange　membrane　(PEM)　fuel　cell/electrolyzer-based　regenerative　hybrid　power　system　modeling　and　energy　management　for　automotive　application.　In　the　regenerative　hybrid　power　system,　the　fuel　cell　acts　as　the　main　power,　and　the　battery,　supercapacitor,　and　electrolyzer　consist　of　a　hybrid　energy　storage　system　(HESS)　to　provide　and/or　reclaim　the　extra　power.　To　effectively　distribute　the　hybrid　power,　the　load　power　demand　of　the　automobile　is　handled　by　using　the　wavelet　transform　based　on　the　power　change　rate.　The　supercapacitor　copes　with　the　high　power　change　rate　load　demand,　and　the　low-slope　portion　is　balanced　by　the　fuel　cell/electrolyzer　and　battery.　To　reduce　the　fuel　consumption　online,　an　improved　rule-based　energy　management　strategy　(EMS)　depending　on　dynamic　programming　(DP)　allocation　of　fuel　cell　power　and　battery　state　of　charge　(SOC)　is　developed,　and　an　electrolyzer　operation　strategy　is　also　designed.　The　numerical　simulation　is　implemented　to　test　the　proposed　rule-based　EMS,　and　the　results　indicate　that　the　real-time　control　keeping　93.8%　fuel　consumption　performance　compared　with　the　off-line　global　optimization　solution　in　a　given　driving　cycle.　(c)　2020　American　Society　of　Civil　Engineers.