Abstract: To investigate the effect of cerium oxide (CeO₂) etching on the surface morphology of diamond, the diamond single crystals and cerium oxide powders were mixed in the ratio of 1:5 by mass and etched under the N₂ atmosphere. The effect of cerium oxide powder etching on the surface morphology of diamond was investigated by characterizing and analyzing the surface morphology, etching depth, and phase composition of the diamond after etching. The effect of etching on the holding force between the diamond and bond was also evaluated by the flexural strength of the diamond specimens with the copper-based bond. The results show that the cerium oxide can successfully etch the surface of diamond single crystal selectively. As the temperature increases, the etching depth of each crystalline surface of diamond deepens, and under the same conditions, the etching depth of cerium oxide on the diamond (100) surface is greater than that on the diamond (111) surface. At the etching temperature of 900 ℃, the etching depth of diamond (111) surface is 753.23 nm and that of (100) surface is 1.60 μm. The compressive strength of the diamond single crystal etched by cerium oxide at 900 ℃ in the N₂ atmosphere is lower than that of the diamond etched without etchant in the N₂ atmosphere, but higher than that of the diamond etched without etchant in the air atmosphere and the diamond etched by cerium oxide directly in the air. Compared with the untreated diamonds, the flexural strength of the copper-bonded diamond specimens after cerium oxide etching is improved.