It＇s　proved　that　the　physical　meaning　of　the　electrical　average　temperature　rise　of　series　LED　array　system　tested　by　electrical　temperature　sensitive　parameter　(TSP)　method　is　the　arithmetic　mean　of　the　temperature　rises　of　all　sub-LEDs　in　the　system.　Based　on　this　relationship,　a　novel　method　to　evaluate　the　temperature　distribution　of　series　LED　systems　by　scan　measurement　and　recursive　calculation　is　proposed　in　this　paper.　Transient　heating　response　measurements　of　GaN　based　high　power　LED　arrays　are　presented　to　provide　experimental　verification　for　this　method.　The　results　show　that　this　method　is　real-time　valid　and　package　form　independent.　The　error　between　the　results　of　individual　measurement　and　this　proposed　method　is　less　than　+/-　2　degrees　C.