To　construct　contact　stiffness　of　the　ball　linear　guides　model,　mechanics　and　deformation　of　the　contact　surface　between　the　ball　and　raceway　based　on　Hertz　contact　theory　were　analyzed.　The　change　of　ball＇s　contact　angle　under　loading　was　considered.　The　relationship　of　contact　force　and　elastic　deformation　of　the　single　ball　was　deduced.　From　this,　The　relationship　of　external　load　and　elastic　deformation　of　ball　linear　guides　was　deduced.　Tooking　the　NSK　ball　linear　guides　as　objects,　the　simulation　of　the　proposed　model　was　anylazed.　The　guide＇s　critical　load　under　different　preloads　were　calculated.　The　change　of　guide＇s　contact　stiffness　were　analyzed　when　the　external　load　was　larger　than　the　critical　load　and　less　than　the　critical　load.　By　comparing　the　data　on　the　NSK　official　website,　the　proposed　model　and　the　theoretical　analysis　are　reasonable.　©,　2015,　Beijing　University　of　Technology.　All　right　reserved.