In this paper, the author gives and analyses the forms and characteristics of the plane harmonic waves in the medium model founded by Men Fulu in which the effect of the viscosity of the fluid has been discussed. It is found out that there are four kinds of plane wave in the medium:first P wave, second P wave, first S wave and second S wave, which are all nonhomogeneous waves. And there are interference effects among them. Their attenuation and phase velocity are determined by the medium parameter, frequency, boundary conditions and source.
It is discussed in detail that P wave and SV wave are incident on the medium Ⅱ, seimispace of the porous medium, from the medium Ⅰ, elastic seimi-space. When SV wave is incident on the medium Ⅱ vertically, some numerical results have been obtained. The theories of propagation of wave in porous media have some significance for observing and explaining precursors of earthquake especially for oil exploration. The effect of viscosity of fluid that the second S wave is simulated must be considered in some acoustic fields and supersonic analogous experiment.