In　this　paper,　we　propose　a　protocol　for　generating　N-qubit　Greenberger-Horne-Zeilinger　(GHZ)　states　in　a　superconducting　system.　The　physical　model　contains　N　superconducting　flux　qubits　and　a　cavity,　where　the　N　superconducting　flux　qubits　are　coupled　to　the　cavity　simultaneously.　The　preparation　of　GHZ　states　can　be　realized　in　one　step　by　applying　a　pair　of　classical　fields　to　each　qubit.　The　protocol　is　promising　for　generating　N-qubit　GHZ　states　because　the　operation　time　is　independent　of　the　number　of　the　qubits　in　the　strong　drive　regime.　Furthermore,　we　consider　the　effects　of　random　noise　and　decoherence,　and　numerical　simulations　show　that　the　protocol　is　insensitive　to　these　disturbing　factors.　Therefore,　the　protocol　may　be　useful　in　the　generation　of　GHZ　states.