Hydrophilic　polymer　coatings　on　artificial　implants　generate　excellent　tribological　properties.　The　friction　properties　of　polymer　coatings　are　affected　by　salt　ion　factors.　Herein,　the　atomic　force　microscopy　(AFM)　was　used　to　show　that　the　superlubricity　was　achieved　between　poly(vinylphosphonic　acid)　(PVPA)-modified　Ti6Al4V　and　polystyrene　(PS)　microsphere　probe　lubricated　with　monovalent　salt　solutions　(LiCl,　NaCl,　KCl,　and　CsCl).　Considering　that　adhesion　is　an　important　cause　of　friction　changes,　the　AFM　was　further　utilized　to　obtain　adhesion　between　friction　pairs　in　different　salt　solutions.　The　results　indicated　that　the　larger　the　cation　radius　in　the　lubricant,　the　smaller　the　adhesion,　and　the　lower　the　friction　coefficient　of　the　PVPA　coating.　The　electrostatic　interaction　between　the　PVPA　and　one-valence　cations　in　lubricants　was　analyzed　by　the　molecular　dynamics　(MD)　simulation　as　it　was　found　to　be　the　main　influencing　factor　of　the　adhesion.　Combined　analysis　results　of　friction　and　adhesion　indicated　that　by　adjusting　the　size　of　cation　radius　in　lubricant,　the　adhesion　between　the　tribo-pairs　can　be　changed,　and　eventually　the　magnitude　of　friction　can　be　affected.　This　study　opens　up　a　new　avenue　for　analyzing　the　friction　characteristics　of　hydrophilic　polymer　coatings　from　the　perspective　of　intermolecular　forces.