A procedure for preparing a nanofluid that a solid-liquid composite material consists of solid nanoparticles with sizes typically of 1-100 nm suspended in liquid was proposed. By means of the procedure, Cu-H2O nanofluids with and without dispersant were prepared, whose sediment pho-tographs and particle size distribution were given to illustrate the stability and evenness of suspension with dispersant. The viscosity of Cu-H2O nanofluid was measured using capillary viscometers. The mass fractions(w) of copper nanoparticles in the experiment varied between 0.04% and 0.16% with the temperature range of 30-70 ℃. The experimental results show that the temperature and SDBS concentration are the major factors affecting the viscosity of the nano-copper suspensions, while the effect of the mass fraction of Cu on the viscosity is not as obvious as that of the temperature and SDBS dispersant for the mass fraction chosen in the experiment. The apparent viscosity of the copper nano-suspensions decreases with the temperature increase, and increases slightly with the increase of the mass fraction of SDBS dispersant, and almost keeps invariability with increasing the mass fraction of Cu. The influence of SDBS concentration on the viscosity of nano-suspension was relatively large comparing with that of the nanoparticle concentration. A procedure for preparing a nanofluid that a solid-liquid composite material consists of solid nanoparticles with sizes typically of 1-100 nm suspended in liquid was proposed. By means of the procedure, Cu-H2O nanofluids with and without dispersant were prepared, whose sediment The viscosity fractions of Cu-H2O nanofluid was measured using capillary viscometers. The mass fractions (w) of copper nanoparticles in the experiment varied between 0.04% and 0.16% with the temperature range of 30-70 ° C. The experimental results show that the temperature and SDBS concentration are the major factors affecting the viscosity of the nano-copper suspensions, while the effect of the mass fraction of Cu on the viscosity is not as obvious as that of the temperature and SDBS dispersant for the mass fraction chosen in the experiment. The apparent viscosity of the copper nano-suspensions de creases with the temperature increase, and increase slightly with the increase of the mass fraction of SDBS dispersant, and almost keeps invariability with increasing the mass fraction of Cu. The influence of SDBS concentration on the viscosity of nano-suspension was relatively large comparing with that of the nanoparticle concentration.