This　paper　analyzes　the　degradation　of　the　electrical,　optical　and　thermal　characteristics　of　the　light-emitting　diodes　(LEDs).　Two　types　of　LEDs　which　are　defined　as　sample　A　and　sample　B　are　tested.　Their　electrical,　optical　and　thermal　characteristics　have　been　continuously　monitored　during　the　test.　The　results　of　our　analysis　demonstrate　that　ohmic　contacts　and　resistivity　of　bulk　are　stable　over　stress　time;　the　die　attach　materials　of　sample　B　get　worse,　but　the　active　layer　is　better　than　sample　A;　the　depletion　region　of　sample　A　is　getting　worse　and　sample　B　is　stable.　The　analysis　above　offers　a　new　method　to　find　which　part　degrades　seriously.　©2009　IEEE.