With increasing applications of Magnetorheological Finishing (MRF) in the field of ultra-precision manufacturing, enhancement of the efficiency of MRF is imperative. To address this requirement, a technique based on pH adjustment was developed in this paper, which in turn, optimized the properties of the polishing slurry. The dispersion behavior of polished particles and the rheological characteristics of the polishing slurry were investigated via scanning electron microscope, particle-size analysis, and Zeta potential test. The results demonstrate that an adjustable pH facilitates the dispersion of nanoparticles. A pH value of 12 has been identified to be the most suitable for the dispersion of the polishing particles. The absolute value of the Zeta potential is observed to be 33.28 mV and the particles diameter of D50 is detected to be 260 nm under this pH. After polishing of fused silica, the alkaline MRF fluid is demonstrated to not only lead to superior material removal rate, with the corresponding peak removal rate and volumetric removal rate increasing by 87% and 66%, respectively, but also achieve a precise level of surface roughness.