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The acoustic liner of the nacelle of an aeroengine is the most important noise reduction device of the engine. In order to establish an accurate impedance model related to the structure and acoustic performance of the acoustic liner, it is necessary to analyze the acoustic impedance eduction technology of the liner. Two liner impedance eduction techniques, in-situ impedance eduction method and straightforward method, were compared and analyzed. Same flow tube acoustic test platform, liners with controllable deviation, and repeatability test of impedance measurement were used to ensure the subjectivity of the comparison. Two aforementioned impedance eduction methods were used to obtain the acoustic impedance of both single-degree-of-freedom acoustic liner and double-freedom liner. It indicated that the measurement results from the two impedance eduction methods were well matched with each other in frequency of both mid-range and high-range, and there were significant differences in the low-frequency ranges. Compared with the straightforward method, the in-situ method was more applicable for a wider range of frequency, and it could also identify the local acoustic impedance characteristics of the acoustic liner. In-situ method was less limited for the size of acoustic liners, however, the breaking of the liner structure was inevitable for such method, which means such method was more suitable for traditional liners. The straightforward method could measure the overall impedance characteristics of the acoustic liner. It could also obtain accurate impedance results in both middle and high frequency range without breaking liner structures, and therefore it could be used in a wider range of plate-type sound-absorbing materials. [ABSTRACT FROM AUTHOR]