Abstract: The impedance change of 3PE coating, PE heat shrinkable sleeve and/or shrinkable tape that have been widely used for external corrosion control of buried steel pipeline with the electrochemical impedance spectroscopy (EIS) method is measured. By means of fitting impedance spectrum with appropriate circuit, the change law of resistance values of 3 kinds of polyethylene coatings under different experimental conditions is obtained. The researchers carry out a study on the anti-electrolyte permeability property and anti-disbonding of the three polyethylene coatings under different cathodic polarization potentials. Result shows that with a negative shift of cathodic polarization potentials and elongation of experimental time, the resistance of samples is reduced obviously, which appears a sharp decrease under beneath polarization potential. This answer displays that too great a negative polarization potential will more easily result in infiltration of electrolytes to coating, causing earlier failure of coating.