Viscoelastic wave equations are derived for both the Biot flow and squirt-flow involved. The relationship between phase velocity or attenuation of viscoelastic wave and macro parameters of the reservoir is clarified in a porous extensive dilatancy anisotropy medium. Numerical models clearly demonstrate that the viscoelastic property of rocks, not the squirt-flow, causes the dispersion and attenuation in the low-frequency range. The attenuation of the quasi SV-wave, SH-wave and the quasi P-wave depend strongly on the directions of permeabilities. Furthermore,the trends of attenuation of the quasi P-wave fast and the quasi SV-wave are inversed in both the high-frequency and Iow-frequency ranges. Our numerical result is in agreement with the experimental result that was carried out for the Biot/Squirt model by Jorge [Geophys. 65(2000) 202]