Abstract: In this paper, the marine sediment is regarded as a wet granular media. The propagation of sound in wet close granular media can excite two expand waves and a rotation wave. When these characteristics are considered and assume that the interface of sea water and sediment is a plane, the expression of reflection coefficient is derived. In case of the loose granular media, the reflection coefficient is simplifyed the result obtained is identical with that obtained by seniors from phenomenon theory. The theoretical result agrees quite well with the practical data.