Surface-enhanced　Raman　scattering　(SERS)　has　been　applied　in　a　range　of　fields　for　its　high　sensitivity　and　its　potential　applications　in　several　critical　social　areas.　Reproducible　fabricating　the　SERS　substrates　in　large　scale　and　low　cost　has　been　one　of　the　hot　topics　in　SERS　researches.　In　this　paper,　we　assembled　the　solution　processed　gold　nano　clusters　with　the　diameter　less　than　5　nm　into　the　randomly　distributed　gold-nanoislands　by　optimizing　the　annealing　process.　We　found　that　the　assembling　process　was　slow　and　could　be　finely　controlled　as　the　annealing　temperaturewas　within　the　range　of　150　similar　to　210　degrees　C.　By　controlling　the　assembling　process,　we　can　reproducibly　fabricate　a　kind　of　homogeneous　SERS　substrate　with　high　density　of　＂hot　spots＂　in　large　area.　These　SERS　substrates　had　intense　surface　enhanced　Raman　scattering　to　the　monolayer　adsorbed　on　the　surface　of　the　gold-nanoislands,　and　yielded　a　global　enhancement　factor　as　large　as　10(6)similar　to　10(7)　for　the　samples　annealed　at　150　similar　to　210　degrees　C.　We　found　that,　under　the　same　conditions,　the　gold　nano　clusters　were　firstly　fused　into　tiny　gold-nanoislands　with　the　diameter　of　10　similar　to　20　nm　as　the　annealing　temperature　was　within　the　range　of　150　similar　to　180　degrees　C.　As　the　annealing　temperature　was　increased　to　190　similar　to　210　degrees　C,　the　matrix　of　tiny　gold-nanoislands　(10　similar　to　20　nm)　and　large　gold　nanoislands　(50　similar　to　70　nm)　could　be　formed.　The　spectral　characterization　has　shown　that　the　samples　consist　of　the　matrix　of　tiny　and　large　gold-nanoislands　have　a　higher　global　enhancement　factor　than　the　samples　consist　of　barely　tiny　gold-nanoislands.　At　220　degrees　C,　the　gold　nanoclusters　completely　fused　into　large　gold-nanoislands.　However,　the　gaps　between　the　large　gold-nanoisland　also　increased　with　the　fusing　process,　which　induced　an　exponential　decay　of　the　intensity　of　the　electromagnetic　field　between　the　gold-nanoislands.　As　a　result,　the　samples　annealed　at　220　degrees　C　has　the　lowest　SERS　enhancement　factor.　In　this　work,　we　demonstrated　the　mechanism　of　how　low-temperature　annealing　process　affects　the　assembling　of　the　gold　nanoclusters.　We　also　showed　the　relationship　between　the　morphology　of　the　gold-nanoisland　and　the　SERS　properties.　We　provided　a　facial　rout　for　controllable　fabricating　the　high　quality　SERS　substrates,　which　has　potential　applications　in　the　future.