Silver　nanofluids　with　three　different　volume　fractions　are　prepared　by　a　one-step　chemical　reduction　method　(Ultrasound-assisted　Membrane　Reaction　(UAMR)).　The　convective　heat　transfer　and　friction　characteristics　of　silver　nanofluid　in　micro-pin　fin　heat　sink　are　investigated　experimentally.　The　results　indicate　that　the　pressure　drops　of　nanofluids　with　different　volume　fractions　have　little　difference.　Compared　to　the　base　fluid　(polyvinylpyrrolidone　(PVP)　solution),　the　pressure　drop　of　nanofluids　increases　slightly　at　the　same　volume　flow　rate.　When　the　flow　rate　is　small,　the　increment　is　not　obvious.　The　introduction　of　surfactant　increases　the　fluid　viscosity,　so　the　pressure　drops　of　nanofluids　are　larger　than　those　of　pure　water,　under　the　same　flow　rate.　However,　the　maximum　difference　is　no　more　than　10%.　The　volume　fraction　of　silver　nanoparticles　significantly　affects　the　convection　heat　transfer　coefficient　of　micro-pin　fin　heat　sink.　The　presence　of　nanoparticles　improves　significantly　the　heat　transfer　performance.　However,　high　viscosity　of　the　nanofluids　hinders　the　heat　transfer　strengthening　effect　of　nanofluids.　In　the　present　work,　when　the　volume　fraction　of　silver　particles　reaches　to　0.012%,　the　thermal　resistance　of　nanofluid　gradually　becomes　lower　than　that　of　deionized　water,　which　indicates　the　integrated　heat　transfer　enhancement　of　nanofluids.