Abstract: On this paper, a method of effectively calculating the acoustic attenuation coefficient for a fluid sea-bottom with high sound speed is presented. The method is formulated on the base that the fractional part of the attenuation coefficient contributed by the water-column varys slowly with different normal modes. One of the advantages of the method is that it can remove the effects of the water-column absorption. Furthermore, the method can be used to inverse the sea-bottom acoustic attenuation coefficient in a wider frequency range of f≤2 kHz than the conventional methods (f≤200Hz).