Daylight　is　a　valuable　resource　with　characters　of　both　photometry　and　radiometry,　and　window-to-wall　ratio　(WWR)　is　a　crucial　building　envelope　element　that　decides　the　indoor　luminous　and　thermal　environments.　Due　to　the　traditional　utilize　of　external　shadings　and　lack　of　appropriate　design　standard　for　buildings　in　China　low　latitude　region,　this　study　proposes　a　workflow　for　optimizing　WWR　with　sunshades　by　considering　both　day　lighting　performance　and　energy　consumption.　The　reference　WWR　is　firstly　decided　based　on　the　requirements　of　daylighting　standards　by　using　Radiance　for　standard　room　without　external　shading,　and　the　reference　annual　cooling　load　of　the　whole　building　is　then　calculated　by　EnergyPlus.　A　large　number　of　cases　with　different　WWRs　and　external　shadings　are　calculated　and　energy-saving　and　daylighting　performances　are　finally　verified　with　reference　case.　The　optimal　WWR　value　range　with　different　sunshades　configurations　in　different　orientations　is　that　meets　daylighting　requirement　while　below　reference　annual　cooling　load.　The　results　indicate　that　comprehensive　sunshades　have　the　best　energy　performance　with　the　benefits　of　both　horizontal　and　vertical　ones.　With　a　1.8　m　comprehensive　sunshade,　the　lower　threshold　of　WWR　raises　to　0.40　for　meeting　daylighting　requirement,　and　the　accepted　upper　threshold　of　WWR　range　for　west,　north,　east　and　south-facing　units　could　reach　to　0.56,　0.6,　0.6　and　0.78　respectively.　For　designing　a　building　with　facade　the　same　in　all　orientations,　the　largest　WWR　could　be　set　as　0.7　for　west-east　buildings　and　0.55　for　south-north　buildings　with　1.8　m　comprehensive　sunshades.　The　scenario　has　been　verified　and　this　WWR　optimization　process　could　be　applied　to　different　buildings　in　other　climate　regions.