We　investigate　the　interaction　between　dark　states　and　Rydberg　excitation　blockade　by　using　electromagnetically　induced　transparency　(EIT),　fluorescence,　and　four-wave　mixing　(FWM)　signals　both　theoretically　and　experimentally.　By　scanning　the　frequency　detunings　of　the　probe　and　dressing　fields,　respectively,　we　first　observe　these　signals　(three　coexisting　EIT　windows,　two　fluorescence　signals,　and　two　FWM　signals)　under　Rydberg　excitation　blockade.　Next,　frequency　detuning　dependences　of　these　signals　are　obtained,　in　which　the　modulated　results　are　well　explained　by　introducing　the　dressing　effects　(leading　to　the　dark　states)　with　the　corrected　factor　of　the　Rydberg　excitation　blockade.　In　addition,　the　variations　by　changing　the　principal　quantum　number　n　of　Rydberg　state　shown　some　interesting　phenomena　resulting　from　Rydberg　blockade　are　observed.　The　unique　nature　of　such　blockaded　signals　can　have　potential　application　in　the　demonstration　of　quantum　computing.　(C)　2013　AIP　Publishing　LLC.