The corrosion process of germanium single crystal in SiO₂ polishing solution containing HNO₃ and under the condition of chemical mechanical polishing(CMP) was studied. By changing the polishing time, the changing law of the surface state of germanium single crystal was analyzed. The results show that when the pH value of SiO₂ polishing solution is 1~2, there are the forms of Si—OH and Si—O^- in SiO₂ polishing solution; germanium single crystal reacts with nitric acid to form Ge(NO₃)₄. Then, the oxygenate of Ge⁴⁺ will be violently hydrolyzed to generate Ge—OH, and Ge—OH will continue to react in the form of Ge—OH₂⁺. Under the attraction of surface charge, Si—O^- and Ge—OH₂⁺ create Si—O—Ge softening layer on the surface of germanium single crystal, which speeds up the corrosion rate and promotes the degree of surface polishing from the perspective of kinetics. When the polishing time is controlled within 15~20 min, the normal velocity of mechanical polishing and erosion is in equilibrium. After CMP polishing, the surface roughness S_a of germanium single crystal is ≤ 0.8 nm, and there are no scratches and pits under 10x microscope.