Through the numerical analysis of reflection characters of plane multilayer media

we find that multilayer media have the frequency absorbing character （FAC）

implying that its reflection corfficient is zero or minimum at some certain frequency called absorbing frequency （AF）. And there exists some relation between these frequencies and the depth of the interfaces of layers. According to this relation we proposed that the depth of interface can be estimated by zeroes or minimums of reflected wave spectrum and proposed a new method to compensate the attenuation of reflected wave caused by lossy medium. The analysis method in this paper can be applied to the sounnding of earth strata’ s depth.