In　this　paper　a　strengthened　acousto-optic　(AO)　coefficient　of　piezoelectric　crystal　is　proposed.　It　shows　the　influences　of　AO　effect,　electro-optic　(EO)　effect　and　piezoelectric　effect　in　piezoelectric　crystal.　Through　correcting　acoustic　momentum　mismatch　into　sum　of　the　acoustic　and　electric　momentum　mismatch,　the　coupled　wave　equation　group　of　the　surface　acoustic　wave　(SAW)　AO　effect　can　be　changed　as　that　of　SAW　acousto-electro-optic　(AEO)　effect.　A　diffraction　efficiency　formula　of　SAW　AEO　effect　is　given　through　solving　the　equation　group.　The　formula　indicates　that　the　diffraction　efficiency　is　related　to　power　of　SAW,　acoustic　frequency　deviation　and　direct　current　(DC)　voltage.　We　designed　and　manufactured　a　SAW　AEO　device　using　Lithium　Niobate　(LN).　Some　curves　of　relative　diffracted　efficiency　vs　power　of　electric　signals　driving　the　device,　acoustic　frequency　deviation　and　DC　voltage　are　measured.　Experimental　results　are　consistent　with　theory.　SAW　AEO　device　can　be　used　as　a　deflector　or　modulator.　When　it　is　used　as　deflector,　its　bandwidth　is　wider　than　that　of　SAW　AO　deflector.　When　it　is　used　as　modulator,　its　center　frequency　can　be　changed.　SAW　AEO　device　has　smaller　volume,　less　energy　consume　and　is　easy　to　integrate.　It　can　be　used　in　optic　communication　and　real　time　signal　processing,　for　example　correlation,　convolution,　spectrum　analysis　and　optic　vector　calculation　and　so　on.