Several water-based nanofluids were prepared under the action of surfactant by using ultrasonic dispersion method. The absorbency and viscosity of the nanofluids prepared under different conditions were measured and analyzed. The results showed that, when the mass fractions of nanoparticles were 0.2%, the most appropriate surfactants for Al2O3, FeO, γ-Fe2O3 water-based nanofluids were SDBS (Sodium Dodecyl Benzene Sulfonate), ACT (ammonium citrate), CTAB (Cetyltrimethyl Ammonium Bromide), respectively and the optimum mass fractions of the surfactants corresponding to the three nanofluids were 0.2%, 0.1%, 0.2%, respectively, to obtain the best dispersion stability. The optimum ultrasonic condition was 60 min of ultrasonic time under 300 W of ultrasonic power or 90 min of ultrasonic time under 200 W of ultrasonic power, in which the water-based nanofluids had the largest absorbency, the smallest viscosity and the strongest stability. In addition, the greater the size of the nanoparticles the easilier the reunion, and the poorer the dispersion stability was. When the pH value was about 4, the absorbency of Al2O3 nanofluid was larger and the dispersion stability was better. The inherent mechanism of keeping stability of nanofluids was discussed.