In　the　present　paper,　by　applying　the　Lang-Firsov　canonical　transformation　and　the　so-called　non-crossing　approximation　technique,　we　investigate　the　joint　effects　of　the　electron-phonon　interaction　and　an　external　alternating　gate　voltage　on　the　transport　of　a　quantum　dot　system　in　the　Kondo　regime.　We　find　that,　while　the　satellite　Kondo　resonant　peaks　appear　in　both　the　averaged　local　density　of　states　and　the　differential　conductance,　the　main　Kondo　peak　at　the　Fermi　energy　is　greatly　suppressed.　These　results　confirm　the　previous　ones　derived　by　other　methods,　such　as　the　equation　of　motion　solution.　Furthermore,　based　on　the　picture　of　virtual　transition　between　quasi-eigenstates　in　the　system,　we　also　give　a　slightly　different　explanation　oil　these　phenomena.