The　oil-free　scroll　air　compressor　is　a　critical　component　of　fuel　cell　systems.　External　cooling　structures　can　lower　the　discharge　temperature　of　scroll　air　compressors,　maintain　the　purity　of　compressed　air,　and　facilitate　isothermal　compression.　In　this　study,　a　multi-objective　optimization　design　method-based　water-cooled　scroll　plate　structure　is　proposed　for　the　discharge　temperature　reduction.　A　complete　model　of　a　variable　cross-section　scroll　compressor　with　a　water-cooled　scroll　plate　for　simulation　analysis　is　firstly　formulated.　Based　on　network　thermal　resistance　and　response　surface　methods,　a　cooling　channel　thermal　resistance　model　and　a　pressure　loss　model　are　developed.　The　water-cooled　scroll　plate　geometry　parameters　and　coolant　mass　flow　rate　are　optimized　by　multi-objective　genetic　algorithm,　while　the　air　compressor　performance　has　been　simulated.　The　results　show　that　the　coolant　mass　flow　rate　has　the　greatest　effect　on　the　pressure　loss.　The　overall　performance　of　Group　#3　from　Pareto　optimal　solutions　is　relatively　balanced,　demonstrating　better　heat　dissipation　capability　and　lower　pressure　loss.　The　discharge　temperature　was　reduced　by　24.18　K,　the　pressure　loss　was　reduced　by　3.69　%,　and　the　isentropic　efficiency　was　increased　by　10.85　%.　Therefore,　the　proposed　water-cooled　scroll　plate　structure　and　its　optimization　method　can　effectively　balance　the　performance　of　thermal　resistance　and　pressure　loss,　which　is　an　important　way　to　improve　the　isothermal　compression.