A　new　system　for　nanofluid＇s　particle　size　measurement　was　built　based　on　the　dynamic　light　scattering　method.　The　homodyne　scheme　was　used　to　analyze　light　intensity　signal.　SiO2＇s　particle　sizes　were　measured　within　the　SiO2/H2O　nanofluids　with　volume　fractions　of　0.005%　and　0.0025%,　separately.　The　average　deviations　of　the　results　were　1.37%　and　1.39%,　separately.　The　results　can　meet　the　high　accuracy　requirement　of　the　particle　size　measurement　of　nanoparticles.　The　average　particle　sizes　in　two　nanofluids　with　different　volume　fraction　were　same,　and　the　deviations　were　within　the　uncertainty　of　the　experiment.　The　sizes　were　constant　with　time　passed　by,　which　can　prove　the　stability　of　the　nanofluid.　This　method　could　be　used　for　evaluating　the　stability　of　nanofluid.　©　2016,　Science　Press.　All　right　reserved.