NOVELTY - Metal silicon is ground and screened to obtain silicon powder. The silicon powder is immersed in a de-oiling solution. The silicon powder is added to hydrochloric acid, stirred and dried. The dried silicon powder is added to porcelain boat of a tubular furnace, and a mixed gas of argon and oxygen is introduced to the furnace. The tubular furnace is naturally cooled. A complexing agent solution is added to cooled silicon powder and complexed. The hydrofluoric acid is added to silicon powder and leached. The precipitated powder is dried to obtain polycrystalline silicon.    USE - Refinement of metal silicon used for solar battery.    ADVANTAGE - The method provides metal silicon with high purity simply, environmental-friendly and economically, with reduced energy consumption.    DETAILED DESCRIPTION - Metal silicon is ground and screened to obtain silicon powder with diameter of 150-250 meshes. The silicon powder is immersed in a de-oiling solution under an ultrasonic environment. The de-oiling solution contains ethanol, carbon tetrachloride and/or acetone. The silicon powder is added to hydrochloric acid (0.5-3 mol/L), stirred for 30 minutes and dried. The dried silicon powder is added to porcelain boat of a tubular furnace, and a mixed gas of argon and oxygen which is heated with a buffer bottle filled with deionized water (5-10 ml) is introduced to the tubular furnace. The mix ratio of argon and oxygen is 1000:0.5. The tubular furnace is heated at 1200-1400 degrees C for 30-90 minutes, and the introduction of mixed gas is stopped. The vacuum degree of tubular furnace is adjusted to 0.1-1 MPa, and the temperature of the tubular furnace is 1200-1400 degrees C for 30-90 minutes. The tubular furnace is naturally cooled to 80 degrees C or less. A complexing agent solution is added to cooled silicon powder and complexed for 10-30 minutes. The hydrofluoric acid (0.3-1.5 mol/L) is added to silicon powder and leached for 2 hours during stirring and the temperature of the leaching process is 50-90 degrees C. The solution which is the lower layer is discharged from the system. The silicon powder is washed with deionized water through stirring, until the floating silicon powder is precipitated. The precipitated powder is dried at 60-80 degrees C under reduced pressure, to obtain polycrystalline silicon.