Abstract: The adsorption isotherms Of polyethylene glycols (PEG, molecular weights of 400, 1000, 3350, 6000 and 20000), one polypropylene glycol (PPG) and polyoxyethylene-polyoxypropylene block co-polymers (L61, L64 and F68) from water onto silica gel have been determind (at 25℃). Except polypropylene glycol,all the other isotherms can be represented by the Langmuir equation. The calculated results show that for PEG and EO-PO co-polymer the molecular area at limiting adsorption (A) versus the number of EO in the polymer molecules (n_(EO)) is a curve which does not through the origin, If the PEG molecular weight>3000, the A-n_(EO)) curve is approximately a straight line through the origin. On the basis of these results and the cosideration of adsorption of water, it is suggested that the adsorbed molecules lies flat on the surface of silica gel.