As　an　important　connection　part　of　machine　and　foundation,　the　machine-foundation　interface　have　a　critical　effect　on　the　working　accuracy　and　life　of　whole　machine.　The　machine-foundation　interface　is　generated　by　two　kinds　of　materials　(steel　and　concrete),　a　crushed　theory　of　asperity　on　concrete　is　proposed　in　this　paper.　This　theory　hold　that　asperity　on　concrete　will　be　crushed　when　the　load　on　surface　go　beyond　the　limit　of　stress.　This　paper　gave　the　real　contact　area　model　of　concrete-steel　interface,　the　relationship　of　corresponding　normal　contact　load　and　the　real　contact　area　of　single　asperity,　and　the　different　fractal　dimension＇　influence　on　the　contact　quality　of　joint　surface　is　revealed　by　using　MATLAB　simulation　software.