To address the issues of local damage and leakage in geomembranes, which can lead to seepage deformation in the geomembrane cushion, a study on acoustic monitoring of seepage deformationof geomembrane cushion is proposed to be carried out based on the excellent sound transmission properties of geomembranes. A laboratory experimental study on the sound transmission properties of geomembranes and the acoustic characteristics of seepage deformation of geomembrane cushion was conducted using a self-designed testing apparatus. The results show that both PVC and PE geomembranes exhibit a certain degree of sound transmission, with better sound transmission effect for low-frequency sound waves than that for high-frequency sound waves. The acoustic energy of the seepage deformation of geomembrane cushion is mainly concentrated in three frequency bands: low (below 250.Hz), medium (500 to 750.Hz), and high (1 000 to 1 250.Hz), with the highest energy in the low-frequency band. The maximum instantaneous sound wave intensity during the seepage deformation of the geomembrane cushion is 119.29.dB, while the stable sound wave intensity can still be maintained at around 90.dB, both of which are greater than the observation results of the underwater background noise in relevant water areas under undisturbed conditions.