This　paper　develops　a　novel　numerical　model　for　the　calculation　of　dynamic　impedance　of　soil　considering　endbearing　pile　groups　under　vertical　vibration.　The　soil　layer　is　treated　as　a　linear　viscoelastic　material　with　hysteretic　damping.　The　vertical　displacement　is　assumed　to　be　uniform　in　each　individual　pile　in　the　groups　at　the　same　embedment　depth.　Using　separation　of　variables　and　applying　proper　boundary　conditions　at　the　surface　and　rigid　bedrock,　the　governing　equation　of　soil　layer　in　three-dimensional　(3D)　is　first　transformed　into　a　two-dimensional　(2D)　Helmholtz　equation　in　xy　plane,　where　the　solution　in　the　vertical　direction　is　obtained　analytically.　To　solve　this　problem　efficiently　and　accurately,　the　whole　2D　unbounded　soil　is　then　divided　into　a　finite　interior　domain　and　an　infinite　exterior　domain.　The　finite　domain　is　discretized　using　the　finite　element　method　(FEM)　while　an　exact　circular　artificial　boundary　condition　(ABC)　is　developed　to　model　the　infinite　domain.　Finally,　the　effect　of　pile　group　interaction　on　the　dynamic　impedance　of　soil　is　investigated　considering　various　factors,　e.g.,　dimensionless　frequency,　pile　number,　pile　slenderness　ratio　and　relative　distance　between　piles.