The polymer-micelle model, formerly established by Cabane, is revised to develop a new viscosity equation to describe the dependence of dilute solution viscosity on polymer concentration in PEG/SDS aqueous solutions. Two parameters in the new equation were proposed to characterize the influence of the polymer solution viscosity on the added surfactant. The viscosity data of polyethylene glycol (PEG) solutions containing sodium dodecyl sulfate (SDS) were measured by the Ubbelohde dilution viscometer and the new equation proved to be in good agreement with the experimental data.