Aiming at the sound absorption problem of anechoic coating in water seepage state, firstly, the sound absorption coefficient of anechoic coating in infinite water area with steel plate as backing is calculated based on transfer function method and finite element method, anAd the solution results are compared with the analytical result of uniform layered medium to verify the correctness of the solution method. Secondly, the calculation model of cavity containing anechoic coating with different seepage proportion is established to analyze the influence of water seepage on the sound absorption performance of anechoic coating. The calculation results show that within the calculated frequency band, water seepage proportion has different influence characteristics on different frequency bands of anechoic coating, and with the aggravation of water seepage, the peak point of sound absorption moves to medium and low frequency, and the singular value point of sound absorption coefficient moves to high frequency; and the singularity of the valley value of the sound absorption coefficient is mainly due to the change of the cavity resonance mode. The results of this paper can provide some reference for the acoustic performance evaluation of abnormal state of anechoic coating.