Hybrid bilayer membrane consisting of self-assembled alkanethiol and lipid monolayer on gold electrode was fabricated by the paint-freeze method. The interaction of a kind of polyanion, K7Fe^3^+P2W17O62H2 with such bilayer membrane was investigated by cyclic voltammetry and ac impedance. The hybrid bilayer membrane on the gold electrode showed remarkable insulationg property, however, the property was lessened to some extent after interaction with the polyanion. It was found the process was irreversible. It is presumed that the interaction between the polyanion and lipid is an interaction fo K7Fe^3^+P2W17O62H2 with the polar head group of PC, which lessens the interaction among PC polar head groups. The resulting molecular arrangement becomes looser, even some pores are produced.

Key words: HETEROPOLYACID, MERCAPTAN, PHOSPHOLIPID, PHOSPHATE, TUNGSTATE, IRON COMPOUNDS, POTASSIUM COMPOUNDS, CYCLOVOLTAMGRAPH