By　Lyapunov　control,　we　present　a　protocol　to　prepare　entangled　states　such　as　Bell　states　in　the　context　of　cavity　QED　system.　The　advantage　of　our　method　is　of　threefold.　Firstly,　we　can　only　control　the　phase　of　classical　fields　to　complete　the　preparation　process.　Secondly,　the　evolution　time　is　sharply　shortened　when　compared　to　adiabatic　control.　Thirdly,　the　final　state　is　steady　after　removing　control　fields.　The　influence　of　decoherence　caused　by　the　atomic　spontaneous　emission　and　the　cavity　decay　is　discussed.　The　numerical　results　show　that　the　control　scheme　is　immune　to　decoherence,　especially　for　the　atomic　spontaneous　emission　from　to　.　This　can　be　understood　as　the　state　staying　in　an　invariant　subspace.　Finally,　we　generalize　this　method　in　preparation　of　W　state.