TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The concentration of the caustic corrosion solution is 0.1-10 wt.%, preferably 0.5-5wt.%, the caustic corrosion temperature is 20-80 degrees C, preferably 30 degrees C, and the caustic corrosion time is 5-1200 seconds, preferably 20-300 seconds . The caustic corrosion solution refers to aqueous solution containing compound capable of ionizing hydroxyl ion. The compound capable of ionizing hydroxyl ion is sodium hydroxide, potassium hydroxide or ammonium hydroxide. The condition of the acidic corrosion of the acidic corrosion solution includes aqueous solution comprising hydrofluoric acid and a corrosion agent. The concentration of the hydrofluoric acid and corrosion agent in the acidic corrosion solution respectively is 0.1-30 wt.%, preferably 1-15 wt.% and 0.1-70wt.%, preferably 10-60 wt.%. The corrosion agent is nitric acid, phosphoric acid, chromic acid, sulfuric acid or its salt. The corrosion temperature is at -10 to 60 degrees C, preferably -5 to 30 degrees C, and the corrosion time is 120-1800 seconds, preferably 240-720 seconds. The method further comprises performing secondary caustic corrosion for the polysilicon wafer after acidic corrosion in secondary acidic corrosion solution, where the corrosion quantity of the polysilicon wafer based on condition of secondary acidic corrosion is 0.01-1 mg/cm2. The concentration of the secondary caustic corrosion solution is 0.1-10 wt.%, preferably 0.5-5 wt.%, the secondary caustic corrosion temperature is 10-80 degrees C, preferably 15-60 degrees C and the secondary caustic corrosion time is 5-1200 seconds, preferably 20-300 seconds. The second caustic corrosion solution refers to an aqueous solution containing compound capable of ionizing hydroxyl ion. The method further comprises performing secondary acidic corrosion for the polysilicon wafer after secondary caustic corrosion in secondary acidic corrosion solution, where the corrosion quantity of the polysilicon wafer based on condition of secondary acidic corrosion is 0.04-4 mg/cm2. The concentration of the secondary acidic corrosion solution is 0.1-10 wt.%, preferably 0.5-5 wt.%, the secondary acidic corrosion temperature is 10-60 degrees C, preferably 15-60 degrees C, and the secondary acidic corrosion time is 20-800 seconds, preferably 20-300 seconds. The second acidic corrosion solution refers to the aqueous solution containing hydrofluoric acid and hydrochloric acid, where a weight ratio of hydrofluoric acid and hydrochloric acid is 1:(1-5), preferably 1:(1.5-3.5).