The　electrolytic　in-process　dressing　(ELID)　grinding　technology　was　adopted　for　ultra-precision　grinding　experiments　of　GCr15　bearing　steel.　The　experiments　show　that:　grinding　depth,　electrolysis　gap　and　wheel　peripheral　velocity　are　the　main　factors　to　affect　the　surface　quality.　With　the　electrolysis　gap　of　0.5mm,　the　grinding　depth　of　0.1　mu　m,　and　the　wheel　peripheral　velocity　of　18m/s,　the　grinding　effect　can　achieve　optimal　and　the　machined　surface　roughness　can　obtain　Ra0.006　mu　m.