The yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) prepared by atmospheric plasma spraying with different heat treatment period at the temperature of 1250 ℃ were studied in the present investigation.Electrochemical impedance spectroscopy (EIS) was employed to nondestructively examine the impedance and capacitance behavior of free standing YSZ coatings deposited by plasma spray with CMAS (calcium-magnesium alumino-silicate) infiltration.Equivalent circuit was established on the basis of the biomodal structure in coatings.The sintering behavior of the coatings can be reflected by the changes of resistance and capacitance of the coating.By EIS,the microstructure evolution of the coating with CMAS deposits was discussed in detail.