Abstract: The rule of acoustic attenuation when sound propagates in the marine seafloor is worthy of research.As for the high-speed seafloor situation,by using the normal-mode theory,the surface-seafloor acoustic vertical attenuation in shallow water is investigated,and the analytic expression,as well as its upper bound,is derived.The analysis of the simulation and experiment results shows that,as for the high-speed fluid seafloor model,the vertical attenuation is proportional to sound frequency on the whole.At a certain frequency,the water-seafloor sound speed ratio n has a major impact on the vertical attenuation.The smaller the value of n,the greater the vertical attenuation.For the scenario of a large-slope wedge topography with a sound source in the deep-water area,receivers in the shallow-water area,the vertical attenuation is significantly less than its theoretical upper bound.