Rotate　vector　(RV)　reducers　are　typical　deceleration　elements　with　the　outstanding　characteristics　of　small　size,　compacted　structure,　strong　load-bearing　capacity,　and　low　transmission　error,　which　are　widely　applied　in　the　fields　of　industrial　robots,　aerospace,　and　measurement　instruments.　The　cycloidal　gear,　as　the　core　component　in　the　second-stage　drive　of　RV　reducer,　its　tooth　profile　directly　determines　the　general　performance　of　RV　reducer　such　as　meshing　precision,　load-bearing　capacity,　and　riding　stability.　Therefore,　it　is　necessary　to　explore　the　feasible　methods　and　parameters　for　modification　of　cycloidal　tooth　profile.　In　this　paper,　taking　the　CRV-20E　reducer　as　an　object,　firstly,　a　mathematical　model　for　analyzing　contact　stress　and　load　distribution　on　meshing　surface　was　established.　Secondly,　based　on　genetic　algorithm,　a　multi-objective　optimization　for　cycloidal　profile　was　applied　with　maximum　contact　stress　and　load　distribution　coefficient　as　objective　functions,　the　optimal　combination　of　modification　parameters　was　obtained.　Then,　with　the　idea　of　piecewise　modification　and　spline　interpolation　method,　the　cycloidal　profile　was　separated　into　three　segments　of　dedendum,　working,　and　addendum,　which　ensures　conjugated　meshing　in　working　segment,　and　the　reserved　gaps　in　dedendum　and　addendum　can　also　be　remained　flexibility　according　to　the　specific　requirements.　The　mechanism　performance　with　cycloidal　profiles　modified　by　two　proposed　methods　were　systematically　compared　and　discussed.　Finally,　the　finite　element　simulation　verification　was　carried　out.　The　results　indicated　that　both　modification　methods　have　specific　advantages.　This　study　provides　a　theoretical　reference　for　designers　in　the　field　of　gear　profile　optimization　and　underscores　the　critical　implications　for　improving　the　overall　efficiency　and　reliability　of　RV　reducers　in　applications.