In this study, a naturally sourced cutting oil mixture using for the magnetorheological finishing (MRF) as an environmentally friendly carrier liquid. In addition, fuzzy grey relation analysis has been developed to predict and give optimal cutting parameters, the main factors affecting surface quality and material removal rate (MRR) identified. Experimental polishing procedures Ti-6Al-4V alloy were performed to confirm the availability of MRF models of the surface quality and MRR proposed. The fuzzy grey levels of elements to the polishing surface quality, namely the workpiece speed (nw), working distances (K), MRF carrier speed (nMRF) and feed rate (F), were 0.6983, 0.8057, 0.7818, and 0.7817, respectively. The analysis showed that the working distances (K) showed the most remarkable influence on the polishing effect, while the effect of workpiece speed (nw) was the least important. Microscopic observations significantly minimize scratches on the surface. This observation provides an excellent reference value for high surface quality and material removal rate when polishing Ti-6Al-4V alloys.