In　this　paper,　a　composite　technique　of　ELID　grinding　and　mechanical　polishing　is　used　for　ultra-precision　maching　experimental　research.　First,　ELID　grinding　is　adopted　to　pre-process　the　surface　of　WC-Co　cemented　carbide,　obtaining　the　precision　machined　surface　Ra　18nm,　then　the　mechanical　polishing　process　is　implemented.　When　conducting　mechanical　polishing,　the　speed　of　the　turntable　is　set　to　150　∼200　r/min,　and　the　polishing　perssure　is　controlled　in　0.2　∼0.5　N/cm2,　the　polishing　liquid　containing　W1　diamond　grits　is　used　to　process　the　surface　for　about　100　minutes,　aiming　to　achieve　a　rapid　removal.　Then　using　the　polishing　liquid　containing　W0.5　diamond　grits　for　another　100　minutes,　an　ultra-percision　Ra4　nm　is　obtained　by　the　mechanical　polishing　method.　Meanwhile,　the　influence　factors　of　the　surface　roughness　during　mechanical　polishing　process　were　tested,　such　as　abrasive　type,　grain　size,　polishing　liquid　solvents,　polishing　persure,　polishing　time,　etc.