The paper aims tomanufacture a new type of high-hardness silica sol to meet the requirements of high polishing rate and high polishing quality for chemical mechanical polishing (CMP) of silicon wafers. Based on the process characteristics of preparing the silica sol by the constant liquid level polymerization growth method, the hardness and stability of the silica sol are improved by adding the pH stabilizer isopropanolamine during the synthesis process. The transmission scanning electron microscope, infrared spectroscopy, etc. are used to characterize and analyze the colloidal properties such as the composition and morphology of silica sol. Through designing comparative experiments, it is found that the pH stability of the new high-hardness silica sol during polishing is greatly improved compared with ordinary commercial silica sol. The average polishing rates of the three groups of new high-hardness silica sol are 1.580, 1.544 and 1.582 μm/min respectively, which are increased by 17.41%, 17.91% and 18.25% respectively compared with the average polishing rate of ordinary commercially available silica sol. The average surface roughness of the silicon wafer of the new high-hardness silica sol after polishing is only 0.157 nm, and the lowest is 0.132 nm, while the average surface roughness of the silicon wafer of the commercially available ordinary silica sol after polishing is 0.216 nm. Through the detection of the changes in the particle size and morphology of the silica sol before and after polishing, it is found that the new high-hardness silica sol is better than the common commercial silica sol. The new high-hardness silica sol as a polishing abrasive has certain advantages in terms of removal rate and surface roughness and its practical value of the polishing abrasive is verified.