Abstract: Four different concentration TiO2-H2O nanofluids with 20 nm TiO2 were prepared with supersonic oscillator through appending hydrophilic dispersant into deionized water. The viscosities of TiO2-H2O nanofluids and deionized water were measured at different temperatures. The results showed that the viscosities of nanofluids increased apparently compared to the deionized water. And the viscosities varied inversely with the temperature of the TiO2-H2O mixture system. The results also demonstrated that the TiO2-H2O nanofluids were Newtonian fluids.