The　application　range　of　superlubricity　systems　can　be　extended　effectively　by　realizing　an　adjustable　friction　coefficient.　In　this　study,　a　stable　poly(vinylphosphonic　acid)　(PVPA)　superlubricity　system　was　developed　using　sodium　chloride　(NaCl)　solution　as　the　lubricant.　A　sudden　increase　in　the　friction　coefficient　occurred　when　a　trivalent　salt　solution　was　introduced　to　the　base　lubricant　during　the　friction　process.　The　changes　in　surface　microstructure　and　interfacial　molecular　behavior　induced　by　trivalent　cations　were　studied　by　scanning　electron　microscopy　(SEM),　energy　dispersive　spectroscopy　(EDS)　and　molecular　dynamics　simulation.　The　regulation　mechanism　of　trivalent　cations　with　respect　to　the　friction　coefficient　of　the　PVPA　superlubricity　system　was　explored.　Although　La3+　and　Fe3+　in　solutions　exist　in　two　forms　(La3+　and　Fe(OH)(3)),　both　can　destroy　the　stable　coating　structure　through　a　bridging　effect,　resulting　in　a　sudden　increase　in　the　friction　coefficient.　The　ability　of　various　cations　to　attract　the　surrounding　water　molecules　is　an　important　reason　for　the　varying　degree　of　change　of　the　friction　coefficient.　In　addition,　the　degree　of　sudden　increase　in　the　friction　coefficient　is　dependent　on　the　concentration　of　trivalent　cations.　There　is　an　extreme　concentration　at　which　the　maximum　sudden　increase　degree　in　friction　coefficient　can　be　obtained.　This　study　provides　insights　into　the　realization　of　oil-based　superlubricity　through　interface　regulation.