Water-cooled　components　of　air　compressor　provide　a　feasible　way　to　improve　the　performance　of　automotive　fuel　cells.　Due　to　the　large　heat　generation　during　air　compression,　the　efficiency　of　air　compressor　is　normally　not　easily　enhanced.　To　recover　power　and　prevent　excessive　gas　temperature,　this　paper　has　proposed　an　optimized　water-cooled　volute　for　the　turbine-based　air　compressor　used　for　automotive　fuel　cells.　Firstly,　a　three-dimensional　numerical　model　of　the　volute　integrated　with　impeller　has　been　developed,　upon　comparison　with　the　measured　isentropic　efficiency　and　pressure　ratio,　the　mean　absolute　errors　were　found　to　be　0.0669　and　0.0117,　respectively.　Then,　a　closed　flow　passage　on　the　volute　outer　wall　is　constructed　to　form　an　initial　watercooled　volute　structure.　Numerical　simulation　analysis　is　then　conducted　on　the　initial　water-cooled　volute　under　different　cooling　water　inlet　conditions.　The　Box-Behnken　method　is　used　to　generate　the　design　space　for　the　water-cooled　volute　structure,　and　a　response　surface　model　is　fitted　using　a　second-order　function.　The　response　surface　model　is　then　used　as　the　objective　function　of　multi-objective　genetic　algorithm　to　perform　global　optimization　and　generate　the　Pareto　front.　The　combinations　of　parameters　for　the　water-cooled　volute　structures　are　determined　from　the　optimal　solution　set.　The　results　showed　that　the　isentropic　efficiency　of　the　optimized　water-cooled　volute　was　improved　by　12.43　%　compared　to　the　original　volute,　and　the　outlet　gas　temperature　was　reduced　by　1.29　%　compared　to　the　initial　water-cooled　volute.　The　proposed　water-cooled　volute　and　its　design　method　can　enhance　the　overall　performance　of　the　air　compressor　for　automotive　fuel　cells.