51　V　high　voltage　LED　(HV　LED)　was　designed　and　fabricated.　Firstly,　the　HV　LED　was　tested　by　large　current　attack,　then　the　damage　reason　was　analyzed.　The　key　part＇s　thermal　parameters　distribution　model　of　HV　LED　was　simulated　by　using　finite　element　analysis　software　ANSYS,　and　the　steady　distribution　of　temperature　was　achieved.　By　analyzing　the　infrared　thermal　image,　the　reason　of　HV　LED　failure　after　large　current　attack　was　gotten.　The　core　particle　electrode　burned　at　the　connection　part　which　was　thin　and　narrow,　so　the　resistance　was　large.　It　provided　a　good　reference　for　the　sequence　design　of　more　reliable　HV　LED.　Meanwhile,　the　chips　were　packaged　into　white　lamp　with　color　temperature　of　5000　K　and　blue　lamp,　respectively.　The　thermal　resistance　of　the　white　lamp　was　about　4°C/W　higher　than　the　blue　lamp　without　phosphor　coating,　and　it　was　also　higher　than　the　conventional　1　W　LED.　The　deep　groove　structure　and　numerous　interconnected　electrode　structure　of　HV　LED　may　be　the　reason　of　the　thermal　performance　of　high　voltage　LED　worse　than　the　conventional　1　W　LED.