The　contact　stiffness　and　the　error　analysis　have　an　important　effect　on　the　manufacture　and　the　optimization　of　Ball　Linear　Guide　Feed　Unit　(BLGFU).　In　order　to　analyze　the　contact　stiffness　and　linear　errors　or　angle　errors　of　BLGFU,　in　this　paper,　the　contact　stress　and　deformation　mechanics　between　the　ball　and　rail　is　analyzed.　Based　on　Hertz　theory　of　contact　and　theory　of　the　multi-body　system,　a　model　of　the　contact　stiffness　considering　the　changes　in　contact　angle　is　established.　With　the　increasing　of　the　external　load,　the　varying　trend　of　the　contact　deformation　can　be　obtained.　Therefore,　the　motion　accuracy　degradation　of　the　BLGFU　can　be　analyzed.　By　using　a　special　experimental　device　and　test　system　of　the　rolling　linear　guide　worktable,　the　horizontal　contact　stiffness　and　the　vertical　linear　stiffness　are　obtained,　respectively.　By　comparing　the　contact　stiffness　of　the　experiment　dates　and　the　simulation　results,　the　variation　tendency　of　two　curves　is　consisted　and　the　difference　between　the　measured　values　and　the　theoretical　values　is　less　than　18%.　It　is　obvious　that　the　model　of　the　contact　stiffness　considering　changes　of　contact　angle　has　accuracy　and　feasibility.　Thus,　while　external　force　point　locating　at　different　positions;　the　contact　stiffness　and　the　accuracy　analysis　of　the　BLGFU　are　proved　validity　by　simulations.　©　2019,　The　Editorial　Department　of　Journal　of　Harbin　Institute　of　Technology.　All　right　reserved.