Abstract: A suspension of carbon nanotubes as a nanofluids was prepared by dispersing carbon nanotubes into deionized water. The effects of several typical kinds of surfactants such as sodium dodecyl benzene sulfonate (SDBS), hexadecyl trimethyl ammonium bromide (HTAB) and emulsifying agent OP on the stability of the nanofluid were studied by stationary and centrifugal tests with sample morphologies characterized by SEM and TEM. The results showed that the carbon nanotubes can not be dispersed homogeneously in water without surfactant, but the stability of the nanofluid in which a surfactant has been added is enhanced significantly and then it can be kept up for several months. There is a best concentration of surfactant to make the stability optimal, and a best stability is available if using OP as surfactant.