Coupled　wave　equation　group　of　surface　acoustic　wave　(SAW)　acousto-electro-optic　(AEO)　effect　are　given　and　correlative　conversion　efficiency　formula　is　obtained.　An　collinear　SAW　AEO　modulator　with　xy-cut　lithium　niobate　(LN)　substrate　is　made.　Curves　of　relative　conversion　efficiency　vs　electric　power,　direct　current　(dc)　voltage　and　frequency　are　measured.　Additional　dc　voltages　can　change　the　center　frequency　of　the　modulator.　This　device　has　applications　in　optic　signal　processing　and　optic　communication.