Abstract: The effects of the chain length of POE prepared from monodispersed polyoxyethylenated n-dodecyl alcohols on the thermodynamic properties,surface adsorption and micelle ?formation of mixed surfactants were studied.Experimental results indicate that the assumption of ideal mixing for the homologous mixtures appears reasonable.The surface adsorption Γ_∞ and surface pressure ΠCMC of mixed solution are increased with the increase of distribution coefficient resulting in a close molecular orientation at interface.The molecules of the adducts with short POE chain are dominated both in mixed adsorbed layers and in micelles. The amounts of micelle solubilization of in ethylbenzene may be expressed in linear relation.Detergency performence of mixed solutions of C₁₂E_n with wide distribution in POE chain length is surperior to that of monodispersed or narrow distributed C₁₂E_n,but the effect is not noticeable beyond a certain range of distribution.