Light　emitting　diode　(LED)　is　now　widely　used　in　many　fields　including　traffic　lights,　vehicle　backlights　and　liquid　crystal　display　(LCD)　displays　because　of　their　long　life,　good　illumination　efficiency　and　low　energy　consumption.　For　the　high　power　LED　street　lamp,　a　low　operating　temperature　is　essential　for　LED　chips.　However,　it＇s　waste　and　meaningless　to　increase　the　size　of　heat　sink　for　high　power　LED　street　lamp　immoderately.　In　this　paper,　structure　optimization　of　heat　sink　is　studied　on　the　condition　that　the　heat　sink　is　sufficient　for　cooling　demand　of　196W　LED　street　lamp.　1/7,　2/7　and　3/7　length　diminution　of　the　heat　sink　are　studied　respectively.　Results　show　that　temperature　of　plate　surface　is　increased　16°C　with　3/7　bulk　and　weight　reducing.　And　cross-sectional　shape　optimization　of　fin　is　also　studied.　The　result　show　that　the　bulk　and　weight　of　fins　are　reduced　over　50%　with　only　0.42°C　temperature　rise.　The　results　of　this　work　provide　useful　guidelines　for　thermal　management　of　the　heat　sink　without　affecting　the　cooling　demand　of　high　power　LED　street　lamp.　©　2011　IEEE.