Intermolecular interaction between PEG monostearate with two ethylene glycol units (N=2) and several polymer monolayers at air/water interface was investigated. For polymer monolayers, poly(methyl methacrylate) (PMMA) and poly(isopropenyl acetate) (PIPA) were spread on the distilled water. It was observed that the positive or negative deviation behavior between the mean surface area and the composition of the mixed monolayers in the condensed state is in good agreement with the miscibility behavior of the blends of the component polymers in the bulk state.