This　paper　proposes　a　decoherence-immune　scheme　for　generating　highly　entangled　states　for　two　atoms　trapped　in　a　cavity.　The　scheme　is　based　on　two　resonant　atom-cavity　interactions.　Conditional　upon　the　detection　of　no　photon,　the　two　atoms　may　exchange　an　excitation　via　the　first　resonant　interaction,　which　leads　to　entanglement.　Due　to　the　loss　of　the　excitation,　the　two　atoms　are　in　a　mixed　entangled　state.　With　the　help　of　an　auxiliary　ground　state　not　coupled　to　the　cavity　mode,　the　state　related　to　the　excitation　loss　is　eliminated　by　the　detection　of　a　photon　resulting　from　the　second　resonant　interaction.　Thus,　the　fidelity　of　entanglement　is　almost　not　affected　by　the　decoherence.