It　is　known　that　mechanical　connections　have　great　influence　on　the　dynamic　characteristic　of　the　assembly.　In　existing　methods,　the　torsional　stiffness　of　the　robotic　joint　is　calculated　only　considering　the　stiffness　of　components　of　the　system,　which　largely　reduces　the　prediction　accuracy　of　the　joint　stiffness.　In　the　paper,　to　predict　the　joint　stiffness　more　accurately,　a　model　is　proposed　considering　influences　of　the　stiffness　of　all　connections　existed　in　a　joint　system.　The　normal　and　tangential　stiffness　of　the　contact　surface　of　each　connection　are　calculated　by　combining　the　equilibrium　analysis　of　the　force　and　the　fractal　theory.　Then　the　total　stiffness　of　one　robotic　joint　can　be　modelled　by　putting　the　torsional　stiffness　of　all　connections　and　that　of　the　RV　reducer　and　gear　pair　in　parallel.　To　verify　the　proposed　model,　its　simulation　result　is　compared　to　the　stiffness　based　on　the　previous　technique　without　considering　the　influence　of　connections.　The　comparison　result　shows　that　the　proposed　model　can　improve　the　stiffness-prediction　accuracy.　This　study　can　be　extended　to　the　stiffness　modeling　of　other　joint　systems　and　provides　a　theoretical　basis　for　the　dynamic　analysis　of　the　robotic　system.　Copyright　©　2019　ASME.