The laconic calculating formulae of arbitrary multiple-layer model’s acoustic characteristics are introduced with sound transmission theoretics in multilayer mediums. Taking properties of viscoelastic material in account, the sound absorption characteristics of multiple-layer model covered with viscoelastic material underwater are calculated using formulae deduced. By numerical analysis, the relation between absorption model and material parameters is simulated and the effect of proportion among layers’ natural impedance on acoustic characteristics of sound absorption model is analyzed. Then the method of designing sound absorption model by multiple-layer structures each layer natural impedance is studied. The result is of significance to devising sound absorption material and model.