China　actively　promotes　the　construction　of　3　million　square　kilometers　of　marine　territory,　and　is　vigorously　building　the　Xisha　and　Nansha　islands　in　the　south　China　sea　at　present.　The　climate　of　islands　and　reefs　in　the　sea　is　quite　different　from　that　of　continent,　and　is　featured　by　high　temperature,　high　humidity　and　intense　radiation.　Combined　with　the　fact　of　scarce　resources　on　the　island,　it　is　inevitable　to　research　and　develop　low-energy　buildings　under　this　special　climatic　conditions.　In　order　to　determine　the　characteristics　of　the　low-energy　building　envelope　suitable　for　island-reef　climate,　this　paper　analyzes　the　characteristics　of　marine　climate　by　taking　the　measured　data　of　Xisha　as　an　example.　To　study　the　influence　law　of　window-to-wall　ratio　(WWR)　on　energy　consumption,　this　paper　dynamically　simulates　the　annual　refrigeration　consumption　of　one　hotel　to　be　built　on　the　island.　Results　show　that　moisture　load　accounts　for　about　40%　of　the　total　cooling　load.　In　summer,　the　total　cooling　load　of　the　west　room　is　the　highest,　south　room　the　lowest.　Once　WWR　increases　0.1,　the　energy　consumption　increases　3-5　kWh　per　unit　area,　but　the　variety　of　WWR　in　west　and　east　takes　big　effects　on　building　energy　consumption　than　that　in　south　and　north.　The　fractional　energy　saving　of　the　comprehensive　sunshade　is　7%,　the　best　of　all.　The　results　of　this　study　are　intended　to　provide　a　reference　for　the　reasonable　value　of　WWR　in　the　South　China　sea.　©　2018,　Editorial　Board　of　Journal　of　Harbin　Institute　of　Technology.　All　right　reserved.