With numerical evaluation, the effects of different parts of medium, such as elastic, viscous and porous filled with or without fluid, on the wave propagation especially in the range of low frequency band are discussed. Characteristics of seismic wave with Biot coupling are analyzed in the homogeneous and isotropic medium. The results show:(1) the phenomenon of critical porosity exists about the phase-velocity of slow P-wave in and the critical porosity is the blind spot of the phase-velocity of slow P-wave. (2) It is easy to observe slow P-wave in the condition of large porosity and low frequency band. (3) In the range of low frequency band, the phase-velocity of P-and S-wave is independent of penetrability, while the loss factor of P-and S-wave strongly depends on penetrability.