As traditional optical machining technologies can not test and control the subsurface damage in grinding precisely, a new optical machining process was introduced, in which a Magnetorheological Finish(MRF) was used to replace the lapping and to follow the grinding processing. A experiment to remove the subsurface damage caused by grinding was carried out by using a KDMFR-1000F polishing machine and KDMRW-2 water based MR. The experimental results indicate that after rough polishing for 156 min firstly, the 50 μm (depth) subsurface damage of the K9 flat glass has been removed and the surface roughness is 0.926 nm. Furthermore, with a fine polishing for 17.5 min, the 200 nm(depth) glass surface can be removed and the ripples caused by rough polishing are also eliminated, which improves the surface roughness to 0.575 nm. These results show that the propose optical machining processing with MRF can remove effectively the subsurface damage caused by grinding and can provide a high surface roughness below 1 nm.