The　standard　vibration　fatigue　specimens,　made　of　TC11　titanium　alloy,　are　treated　by　laser　shock　peening　(LSP).　The　high-cycle　vibration　tests　are　conducted　to　verify　the　reinforcement　effect,　and　the　fracture　analysis　is　utilized　to　analyze　the　fatigue　mechanism　of　the　treated　specimens.　The　strengthening　mechanism　of　fatigue　performance　is　explained　by　the　experiments　of　microstructure,　residual　stress　and　microhardness.　The　tests　results　show　that　the　fatigue　limit　is　improved　from　483　MPa　to　593　MPa　by　LSP.　Fatigue　crack　of　specimens　treated　by　LSP　initiates　in　the　subsurface　of　0.2-mm　depth　with　a　greater　flatness　area　and　lots　of　second-cracks　and　tight　fatigue　bands.　A　layer　with　nanocrystals　is　generated　on　the　surface　by　LSP,　and　the　size　of　nanocrystal　is　about　40~80　nm.　LSP　introduce　a　great　compressive　residual　stress　in　the　material　with　a　1-mm　thick　plastic　deformation　layer.　The　residual　stress　in　the　surface　can　reach-591.5　MPa,　while　the　surface　hardness　is　increased　by　19%.　The　combined　actions　of　high　structure　refinement　and　high　compressive　residual　stress　are　the　main　causes　of　the　fatigue　performance　improvement,　which　block　fatigue　crack　initiating　and　reduce　crack　growth　rate.