Joint　flexibility　has　a　major　impact　on　the　motion　accuracy　of　a　robotic　end　effector,　particularly　at　high　speeds.　This　work　proposes　a　technique　of　precisely　modeling　the　torsional　stiffness　of　the　rotational　joints　for　the　industrial　robots.　This　technique　considers　the　contacts　that　exist　in　the　joint　system,　which　can　have　a　significant　effect　on　the　overall　joint　stiffness.　The　torsional　stiffness　of　the　connections　that　commonly　exist　in　the　rotational　joints,　such　as　the　belt　connection,　the　connections　using　key,　bolts,　and　pins,　were　modeled　by　combining　the　force　analysis　and　the　fractal　theory.　Through　modeling　the　equivalent　stiffness　for　the　springs　in　serial　and　in　parallel,　the　torsional　stiffness　of　all　joints　for　the　ER3A-C60　robot　were　calculated　and　analyzed.　The　results　show　that　the　estimated　stiffness　based　on　the　proposed　technique　is　closer　to　the　actual　values　than　that　based　on　the　previous　model　without　considering　the　contacts.　The　analysis　is　useful　for　controlling　the　dynamic　characteristic　of　the　industrial　robots　with　the　rotational　joints　while　planning　the　trajectory　for　the　end　effector.