A 3ω method was developed for the simultaneous determination of thermal conductivity and thermal diffusivity of nanofluidsThe principle was presented in the frequency domainThe 3ω system was established by using a Pt wire as the heater and sensorThe system was calibrated by using water with known propertiesThe thermal oscillation signals satisfied the heat conduction equations well in frequency domainIt showed that the microconvection effect of the liquid could be reduced effectively by periodical heatingThe multispherical Brownian motion(MSBW) model was used to predict the thermal conductivities of nanofluidsThe thermal conductivity and thermal diffusivity of TiO2/water and Al2O3/water at different temperatures were proved to increase linearly with the temperature at a low volume fractionThe results showed that temperature dependence played an important role in the enhancement of thermal transport in nanofluidsAt 18—65℃，the enhancement of heat transfer for nanofluids was mainly due to the thermal conductivity increment of water and the microconvection effect.