The precision polishing of optoelectronic materials, such as silicon carbide (SiC) and niobate, poses significant challenges due to their hardness and brittleness. Conventional polishing techniques, including the use of traditional diamond slurries, often result in surface defects, such as scratches and dig marks, compromising the quality and integrity of the materials. In this study, we introduce a nano/sub-micro diamond slurry technology designed to enhance the precision polishing of optoelectronic materials. The developed surface-engineered diamond slurries exhibit improved particle dispersion and controlled size distribution, minimizing particle aggregation and elongation. Polishing experiments conducted on SiC and lithium niobate substrates demonstrate the superior performance of the surface-engineered diamond slurries in terms of material removal rate (MRR) and surface roughness. The MRR achieved with the developed slurries is significantly higher compared to traditional slurries, while the resulting surfaces exhibit reduced dig marks and scratches. Furthermore, the developed slurry technology enables stable and reproducible polishing processes, contributing to reliable and predictable outcomes. This study presents a promising approach for the precision polishing of optoelectronic materials, addressing the limitations of conventional techniques and facilitating the manufacturing of high-quality optoelectronic devices and wafers.