An　effective　protocol　is　proposed　to　generate　three-atom　singlet　states　in　an　atom-cavity　coupled　system.　By　analyzing　the　interactions　between　atoms　and　cavity,　we　first　derive　a　Hamiltonian　with　the　target　singlet　state　approximatively　being　one　of　its　eigenstates.　Then,　to　drive　the　system　from　the　initial　state　to　the　target　state,　we　design　the　waveform　of　the　external　laser　fields　by　Lyapunov　control　method.　The　parameter　selections　are　discussed　based　on　the　experimentally　available　parameters,　and　the　influence　of　the　errors　and　decoherence　on　the　fidelity　are　analyzed.　Numerical　simulations　indicate　that　the　protocol　can　not　only　generate　singlet-state　with　high　speed,　but　also　possess　great　robustness　against　operational　errors　and　decoherence.　Therefore,　the　protocol　may　be　useful　in　the　singlet-state-based　quantum　information　processing.