The　manifold　microchannel　(MMC)　heat　sinks　have　many　advantages　such　as　low　thermal　resistance,　compact　structure,　little　amount　of　coolant,　low　flow　rate,　uniform　temperature　distribution　along　the　flow　direction　and　many　others.　Experiments　are　conducted　to　investigate　flow　characteristics　of　water　through　a　MMC　(width　=　100　μm,　height　=　300　μm),　where　the　Reynolds　Number　range　from　50　to　3500.　Experimental　results　indicate　that　the　critical　Reynolds　Number　transited　from　the　laminar　flow　to　turbulent　flow　is　in　advance.　Furthermore,　the　results　given　by　numerical　simulation　are　almost　the　same　to　those　of　experiments.　Based　on　the　experiments,　the　flow　resistance　empirical　correlations　are　obtained　in　laminar　flow　and　turbulent　flow　regions.