In　the　paper,　the　ELID　grinding　is,　first　of　all,　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　polishing　liquid　with　W1　diamond　grits　is　used　to　process　the　surface　about　100　minutes　after　ELID　grinding,　aiming　to　achieve　rapid　removal.　About　100　minutes　again,　the　ultra-precision　surface,　Ra=4nm,　is　obtained,　by　the　mechanical　polishing,using　the　polishing　liquid　with　W0.5　diamond　grits.　Meanwhile,　on　the　surface　roughness　effects　of　abrasive　type,　grain　size,　polishing　liquid　solvents,　polishing　pressure,　polishing　machining　time　and　so　on,　are　researched　in-depth　for　the　process　of　mechanical　polishing.