Applicable　surface　enhanced　Raman　scattering　(SERS)　active　substrates　require　high　enhancement　factor　(EF),　excellent　spatial　reproducibility,　and　low-cost,　fabrication　method　on　a　large　area.　Although　several　SERS　substrates　with　high　EF　and　relative　standard　deviation　(RSD)　of　signal　less　than　5%　were　reported,　reliable　fabrication　for　large　area　SERS　substrates　with　both　high　sensitivity　and　high　reproducibility　via　low-cost　routes　remains　a　challenge.　Here,　we　report　a　facile　and　cost-effective　fabrication　process　for　large-scale　SERS　substrate　with　Ag　inter-nanoparticle　(NP)　gaps　of　5　nm　based　on　ultrathin　alumina　mask　(UTAM)　surface　pattern　technique:　Such　closely　packed　Ag　NP　arrays　with　high　density　of　electromagnetic　field　enhancement　(＂hot　spots＂)　on　large　area　exhibit　high　SERS　activity　and　excellent　reproducibility,　simultaneously.　Rhodamine　6G　molecules　with　concentration　of　1　X　10(-7)　M　are　used　to　determine　the　SERS　performance,　and　an　EF　of　similar　to　10(9)　obtained.　It　should　be　noted　that　we　obtain　RSDs　about　2%　from　10　random　spots　on　an　area　of　1　cm(2),　which　implies　the　highly　reproducible　signals.　Finite-difference　time-domain　simulations　further　suggest　that　the　enhanced　electric　field　originates　from:　the　narrow　gap,　which　agrees　well　with　the　experimental　results.　The　low　value　of　RSD　and　the　high　EF　of　SERS　signals　indicate　that　the　as-prepared　substrate　May　be　promising　for　highly　sensitive　and　uniform　SERS　detection.