Illumination　properties　in　imaging　system　have　profound　influence　on　the　imaging　characteristics　that　is　ultimately　observed.　Structured　illumination　has　been　applied　widely　to　three-dimensional　microscopic　imaging　for　obtaining　super-resolution　and　sectional　imaging.　It　is　obvious　that　optimized　and　adaptive　structured　illumination　results　in　expected　image.　Three-dimensional　structured　illumination　can　be　produced　by　interference　of　multi-beam　which　is　diffracted　from　a　certain　grating.　Focusing　on　structured-light　formed　by　multi-beam　interference,the　effect　of　phase　grating　modulation　parameters　on　the　properties　of　structured-light　pattern　are　investigated　in　this　work.　Both　simulated　and　experimental　results　show　that　the　phase　grating　has　higher　diffraction　efficiency　and　the　phase　modulation　parameter　of　the　sinusoidal　phase　grating　has　direct　impact　on　the　distribution　of　the　structured　light　pattern.　When　the　phase　modulation　parameter　is　optimized,　the　maximum　modulation　of　structured-light　pattern　in　three-dimension　is　obtained.　Then　we　simulated　the　imaging　of　Fresnel　incoherent　correlation　holography　with　optimized　3D　structured　illumination,　and　presented　the　improved　reconstruction　images.