The　machine　tool　bed　and　concrete　foundation　of　heavy　machine　tools　are　typically　connected　by　anchor　bolts.　The　dynamic　characteristics　of　the　bolted　joint＇s　bed　and　foundation　contact　surfaces　have　an　important　influence　on　the　machining　accuracy　and　service　life　of　the　machine　tool.　This　paper　proposes　a　virtual　material　model　based　on　the　gradient　of　contact　stress　distribution　for　modeling　the　contact　interfaces　between　the　heterogeneous　material　of　the　machine　tool　bed　and　the　foundation.　An　expression　for　the　equivalent　elastic　modulus　of　the　metal-concrete　contact　surface　is　derived　by　considering　the　nonlinear　properties　of　concrete.　Concrete　crushing　is　assumed,　and　the　evaluation　basis　of　critical　deformation　parameters　of　asperity　is　established.　Based　on　Fractal　theory　and　Hertz　contact　theory,　theoretical　models　of　the　elastic　moduli,　Poisson＇s　ratios,　densities,　and　thicknesses　of　the　virtual　material　are　established.　Due　to　the　uneven　distribution　of　contact　stress,　a　gradient　equation　with　virtual　material　parameters　is　obtained　according　to　the　contact　stress　distribution　curve.　Then,　the　contact　surface　is　stratified　based　on　the　virtual　material　parameters.　The　theoretical　model　was　verified　by　simulations　and　experiments.　The　first-order　natural　frequency　error　was　found　to　be　1.3%.　The　proposed　method　provides　a　new　approach　for　modeling　the　contact　between　heterogeneous　materials　of　the　machine　tool　bed-foundation　interface.