Rough　surfaces　have　a　positive　and　important　influence　on　the　mechanical　properties　of　the　joint　surface.　Bolted　joints　are　one　of　the　common　connection　modes,　whose　assembly　stiffness　directly　determines　the　machining　accuracy　of　the　machine　tool.　In　this　work,　considering　the　joint　stiffness　between　connectors,　a　mechanical　model　of　the　joint　surface　considering　the　asperity　interaction　is　established　based　on　fractal　theory.　On　this　basis,　combined　with　the　equivalent　form　of　the　bolted　joint　system,　a　new　stiffness　model　depended　on　strain　energy　method　is　proposed.　Then,　the　correctness　of　the　proposed　model　is　verified　by　experiments.　Finally,　through　the　application　of　FEA,　the　research　on　bolt　tightening　with　different　friction　coefficients　is　completed.　Results　show　that　when　the　stiffness　effect　of　the　bolted　joint　surface　is　neglected,　the　equivalent　stiffness　of　this　system　is　too　large,　exceeding　the　accurate　value　by　more　than　20%.