Subcooled　boiling　has　been　widely　used　in　high　heat　flow　cooling　applications,　such　as　fusion　reactor　divertor　cooling　and　pressurized　water　reactor　core　cooling.　In　this　paper,　the　pressure　drop　characteristics　of　subcooled　water　flowing　in　a　vertical　stainless　circular　tube　are　experimentally　investigated　under　high　heat　fluxes　condition.　The　test　tube　has　an　inner　diameter　of　6　mm　and　a　length-to-diameter　of　44.4.　The　operating　parameters　are　as　follows:　heat　flux　q　=　7.5-12.5　MW/m2,　mass　flux　G　=　6000-10000　kg/(m2s),　pressure　p　=　3-5　MPa,　and　inlet　fluid　temperature　Tb　=　80-200.　The　effects　of　mass　flux,　heat　flux,　pressure,　boiling　number　and　Jacob　number　on　subcooling　boiling　pressure　drop　were　discussed.　The　results　show　that　subcooled　boiling　pressure　drop　increases　with　increasing　heat　and　mass　fluxes　but　decreases　with　increasing　pressure.　The　experimental　data　are　compared　with　the　available　empirical　correlations,　and　it　is　found　that　these　correlations　cannot　well　predict　our　data,　which　may　be　mainly　due　to　the　variations　in　operating　parameters　and　working　fluids.　Moreover,　it　is　observed　that　the　subcooled　boiling　pressure　drop　is　affected　by　diameter　effect.　Therefore,　a　new　correlation　is　proposed　based　on　our　previous　correlation,　in　which　a　correction　term　for　diameter　effect　is　added.　The　new　correlation　can　capture　the　experimental　data　within　±18%　error　bands.　©　All　Right　Reserved.