In　this　paper,　the　superposition　method　is　used　to　investigate　the　complete　temperature　field　of　a　light-emitting　diode　(LED)　packaging　substrate,　based　on　the　results　of　transient　temperature　rise　measurements　and　the　thermal　resistance　coupling　matrix.　The　feasibility　of　use　of　the　superposition　method　in　an　LED　array　with　multiple　packages　has　been　proved　first　by　temperature　comparisons　with　the　simultaneous　operation　of　an　array　(5　x　5)　of　25　high　power　LEDs　mounted　on　a　metal　core　printed　circuit　board　(MCPCB).　Compared　with　existing　approaches,　the　superposition　method　will　measure　the　internal　temperature　of　chip　directly,　accurately　and　nondestructively.　According　to　the　relatively　accurate　and　reliable　self-heating　and　coupling　temperature　rise　data,　optimization　scheme　of　LED　lamp　with　multiple　packages　is　proposed.　The　results　show　that　increasing　the　heat　source　separation　distance　and　improving　the　thermal　conductivity　of　thermal　interface　materials　will　reduce　the　temperature　rise　and　thermal　non-uniformity.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.