Considering　the　shortages　of　existing　bulk　energy　storage　technologies,　to　overcome　the　drawbacks　of　renewable　energies　(i.　e.,　intermittent　and　fluctuation),　a　constant-pressure　pumped　hydro　combined　with　compressed　air　energy　storage　(PHCA)　system　is　proposed　based　on　pumped　hydro　energy　storage　(PHES)　and　compressed　air　energy　storage　(CAES)　technologies.　Firstly,　the　thermodynamic　model　and　economic　model　of　the　system　were　built.　Then,　by　selecting　energy　efficiency　and　total　investment　cost　per　total　output　energy　(ICPE)　as　objective　functions　and　setting　the　hydrosphere　ratio,　the　preset　pressure,　the　pressure　ratio　of　compressor　and　the　efficiency　of　compressor　as　decision　variables,　multi-objective　optimizations　for　systems　of　1　MW,　2　MW　and　5　MW　were　carried　out,　respectively.　The　results　revealed　that　the　system　can　reach　a　relatively　high　system　efficiency　and　a　relatively　low　ICPE　when　the　compressor　efficiency　is　relatively　high　and　values　of　the　hydrosphere　ratio,　the　preset　pressure　and　the　pressure　ratio　of　compressor　are　around　7,　4　MPa　and　2,　respectively.　Furthermore,　with　the　increasing　of　the　capacity　of　the　system,　ICPE　decreases　rapidly.　The　results　could　provide　theoretical　basis　for　the　further　engineering　application　of　this　system.　©　2020,　Science　Press.　All　right　reserved.