This　study　aims　to　optimize　the　chemical　mechanical　polishing　(CMP)　process　for　polishing　the　end　face　of　lithium　niobate　on　insulator　(LNOI)　devices　to　improve　device　performance　and　power　transmission.　LNOI　devices　are　widely　used　in　microwave　signal　processing,　but　high-quality　end-face　polishing　is　crucial　to　minimize　optical　coupling　loss　and　maximize　power　transmission.　A　single-factor　experimental　technique　was　employed　to　optimize　the　CMP　process　parameters　and　determine　the　most　effective　polishing　solution　and　parameters.　Parameters　such　as　load　pressure,　abrasive　ratio,　polishing　solution　flow　rate,　main　disc　speed,　and　transverse　disc　speed　were　optimized,　resulting　in　a　low　surface　roughness　of　the　LNOI　end-face.　The　experiment　identified　that　using　a　cast　iron　disc　for　thinning　the　waveguide　end-face,　followed　by　a　polyurethane　disc　for　fine　polishing,　achieved　the　optimal　polishing　effect.　The　abrasive　used　was　silica　with　a　15　wt%　concentration,　applying　a　pressure　of　17.2　kPa,　a　main　disc　speed　of　20　rpm,　a　polishing　solution　flow　rate　of　3　ml/min,　and　a　transverse　speed　of　10　times/min　for　6　hours.　Surface　morphology　analysis　revealed　that　the　optimized　CMP　process　successfully　reduced　the　surface　roughness　of　the　LNOI　device　from　several　hundred　nanometers　to　0.214　nm,　resulting　in　improved　optical　performance　and　power　transmission.　The　material　removal　rate　achieved　under　these　parameters　was　approximately　60　nm/min.　This　study　provides　valuable　insights　for　the　CMP　polishing　of　other　materials　and　offers　guidance　for　future　research　in　this　area.　©　2023　SPIE.