In　this　paper　we　develop　a　simplified　analytical　solution　for　the　impedance　function　of　viscoelastic　pile　groups　partially　embedded　in　a　layered,　transversely　isotropic,　liquid-saturated,　viscoelastic　soil　medium　under　a　vertical　time-harmonic　load.　In　developing　our　solution,　we　use　the　porous　medium　model　established　by　de　Boer　to　describe　the　soil　and　the　Rayleigh-Love　rod　model　to　describe　the　pile　groups.　To　obtain　the　vertical　impedance　function　of　the　pile　groups,　based　on　a　＂two　pile　model＂　consisting　of　an　active　pile　and　a　passive　pile,　we　first　get　a　displacement　attenuation　function　and　shearing　forces　to　piles　of　the　soil　by　using　a　separation　method　of　variables　to　solve　motion　equations　for　the　soil.　Second,　using　this　displacement　attenuation　function　and　shearing　forces,　we　derive　a　dynamic　interaction　factor　of　pile　to　pile.　Then,　by　means　of　the　dynamic　interaction　factor　and　a　superposition　principle,　we　obtain　the　vertical　impedance　function　of　the　pile　groups.　We　validate　our　model　by　comparing　it　to　the　reported　results　of　purely　elastic　soils.　Finally,　we　conduct　numerical　examples　obtained　from　our　model　to　show　the　effects　of　main　parameters,　such　as　the　non-embedded　length　of　piles,　the　transversely　isotropic　parameter　of　soils,　and　the　liquid-solid　coupled　coefficient　of　soils　on　the　vibration　characteristics　of　a　typical　pile　group.　From　these　analyses,　we　conclude　that　the　dynamic　interaction　factors　of　pile　to　pile　for　single-phase　soils　suggested　by　Dobry　and　Gazetas　are　not　suitable　for　the　vibration　problems　of　pile　groups　in　saturated　soils.　Thus,　it　is　necessary　to　present　corresponding　dynamic　pile-pile　interaction　factors　for　such　problems.　Moreover,　the　non-embedded　length　of　piles,　the　transversely　isotropic　parameter　of　soils,　and　the　liquid-solid　coupled　coefficient　of　soils　have　noticeable　effects　on　the　dynamic　impedance　of　pile　groups,　which　is　valuable　for　pile　foundation　designs.