Abstract: A laser interferometric method was used to determine the frequency and amplitude of water surface acoustic wave caused by an impinging acoustic radiation. The Fourier spectrum of water surface acoustic wave detection signal was studied. Then demodulation method upon the two important acoustic parameters frequency and amplitude of water surface acoustic wave was put forward based on spectrum analysis and demonstrated by a numerical simulation. A simple laser homodyne interferometer was built to detect the water surface acoustic waves. Detection experiments on water surface acoustic waves caused by different driving frequencies and different impinging acoustic pressures were conducted to verify the accuracy of this demodulation method. Preliminary detection experiments for transverse-propagation amplitude attenuation phenomenon of water surface acoustic wave show that as the frequency become higher, the amplitude decrease faster. This work proved that optical interferometric method could accurately determine the frequency and amplitude of water surface acoustic wave.