Planar　process　is　the　foremost　technology　in　fabrication　of　surface　microstructure　which　is　common　in　semiconductor　devices.　In　microstructure　fabrication,　self-assembly　is　a　technology　which　attracts　much　attention　recently.　In　this　article,　based　on　the　micro-phase　separation　and　self-assembly　of　polymer　blends,　a　polystyrene/poly　methyl　methacrylate　(S/PMMA)　blend　film　was　formed　by　solution　co-blending　and　spin　coating.　A　mask　in　which　many　nano-holes　distribute　regularly　was　developed　from　this　film.　The　factors　which　affect　film　pattern　were　researched,　such　as　the　time　of　ultrasonic　processing,　the　rate　of　spin　coating,　the　concentration　of　polymer　blends　solution.　An　alveolate　microstructure　was　fabricated　on　light-emitting-diode　(LED)　surface　by　wet　etching　with　this　mask,　and　the　LED　output　power　increases　by　18%　in　average.