In order to obtain the frequency of water surface acoustic wave exactl y,theoretical analysis and experimental research on water surface acoustic wave interference s ignals are demonstrated.We find the wavelet ridge distribution characteristics of these interference signals:the wavelet ridge points distribute along the scale-time curve which is corresponding to the frequency of water surface acoustic wave,some of which are exactly on the curve,while the oth ers symmetrically distribute on the upper and lower sides.According to this characteristic,a kin d of water surface acoustic wave frequency demodulation method based on wavelet ridge is put forwa rd.The experiment results show this method can accurately determine the frequency of st able-frequency water surface acoustic wave,and the absolute error is less than 1Hz.The detecti on experiment of linear frequency-modulated water surface acoustic wave is also carried out.The resu lts show that wavelet ridge can track the frequency change of water surface acoustic wave in r eal-time,and the rate of frequency variation calculated by the method of wavelet ridge matches with the preseted value,which proves the accuracy of extracting the instantaneous frequency of water surface acoustic wave using the wavelet ridge method.