Featured　Application　A　new　multi-tooth　contact　model　proposed　in　this　study　provides　an　effective　method　to　determine　the　optimal　profile　modification　curves　to　improve　transmission　performance　of　RV　reducers.　Abstract　RV　reducers　contain　multi-tooth　contact　characteristics,　with　high-impact　resistance　and　a　small　backlash,　and　are　widely　used　in　precision　transmissions,　such　as　robot　joints.　The　main　parameters　affecting　the　transmission　performance　include　torsional　stiffness　and　transmission　errors　(TEs).　However,　a　cycloid　tooth　profile　modification　has　a　significant　influence　on　the　transmission　accuracy　and　torsional　stiffness　of　an　RV　reducer.　It　is　important　to　study　the　multi-tooth　contact　characteristics　caused　by　modifying　the　cycloid　profile.　The　contact　force　is　calculated　using　a　single　contact　stiffness,　inevitably　affecting　the　accuracy　of　the　result.　Thus,　a　new　multi-tooth　contact　model　and　a　TE　model　of　an　RV　reducer　are　proposed　by　dividing　the　contact　area　into　several　differential　elements.　A　comparison　of　the　contact　force　obtained　using　the　finite　element　method　and　the　test　results　of　an　RV　reducer　prototype　validates　the　proposed　models.　On　this　basis,　the　influence　of　load　on　the　different　modification　methods　is　studied,　including　a　TE,　the　mechanical　performance,　and　the　transmission　efficiency.　In　addition,　the　proposed　reverse　profile　is　particularly　suitable　for　situations　with　a　large　clearance　and　torque.　This　study　provides　a　reliable　theoretical　basis　for　a　multi-tooth　contact　analysis　of　a　cycloid　profile　modification.