Ice　slurries　of　nanosilica　fluid　at　different　concentrations　were　prepared　by　dispersing　silica　nanoparticles　in　aqueous　solutions　of　either　ethylene　glycol　or　sodium　chloride.　Images　of　ice　crystal　particles　in　ice　slurries　were　obtained　by　a　microscopic　observation　system.　The　resulting　size　distributions　of　ice　crystals　were　compared　to　normal,　log-normal,　Gamma,　and　Weibull　distributions　so　as　to　investigate　nanosilica　effect　on　average　diameter　and　size　distribution　of　ice　particles　and　to　study　dimensional　change　of　ice　particles　during　storage　of　ice　slurries.　The　experimental　results　indicated　that　ice　particle　sizes　were　fitted　well　with　Gamma　distribution　before　and　after　addition　of　nanosilica.　Nanosilica　played　an　important　role　in　grain　refinement　such　that　sizes　of　ice　particles　decreased　linearly　with　increasing　concentrations　of　nanosilica.　When　ethylene　glycol　aqueous　solution　was　base　fluid,　nanosilica　addition　effectively　inhibited　growth　of　ice　particles　during　slurry　storage.　When　sodium　chloride　aqueous　solution　was　base　fluid,　concentration　of　nanosilica　had　to　be　increased　from　0.25%　to　0.75%　for　similar　inhibition　effect.　Therefore,　nanosilica　could　be　used　to　reduce　particle　size　and　to　control　growth　of　ice　crystals,　which　has　an　important　application　for　flow　and　heat　transfer　improvement　of　ice　slurry.　©　All　Right　Reserved.