Abstract: A reverberation model for estimating the average reverberation intensity in layered shallow water is presented. The reverbration intensify is calculated in terms of the ray method for short range and the normal-mode method for long range. The calculation accuracy has been improved by taking into account the effect of complex eigenvalue on the incident mormal-mode field. From the comparason between different scattering models it has been shown that the separable bi-static-backscattering model is acceptable. This makes it possible to calculate reverbration by using only the monostatic-backscattering coefficient and to save greatly the computing time.