In　order　to　find　a　new　way　for　mirror　precision　machining　of　W-Mo　alloy,　precision　grinding　and　ultra　precision　lapping　experiments　were　conducted　using　electrolytic　in-process　dressing　(ELID)　technique.　The　generating　mechanism　of　the　mirror　precision　grinding　of　W-Mo　alloy　was　analyzed.　A　surface　roughness　of　Ra　0.020μm　was　obtained　after　ELID　precision　grinding.　Then,　at　the　optimized　parameters　such　as　lapping　pressure　0.1∼0.3　N/cm2　and　rotational　speed　60∼100　r/min,　a　mirror　precision　surface　roughness　of　Ra　0.012μm　was　achieved.　The　results　proved　that　ELID　technique　guaranteed　the　machined　surface　quality,　and　the　lapping　pressure　as　well　as　the　rotational　speed　were　the　main　influencing　factors　during　ultra　precision　lapping.