The invention relates to a method for purifying silicon, which comprises the following steps: adding molten Na2CO3 in an amount of 10 weight percent based on the weight of the silicon to be purified in the molten silicon to be purified, stirring the melts for 10 minutes, adding a covering agent on the surface of the mixed melt and sealing the mixed melt; monitoring and recording the temperature of the silicon to be purified; when the temperature drops to 1,490 to 1,510 DEG C, reducing cooling rate; when the temperature drops to the melting point of the silicon, keeping the heating power constant; when the silicon begins to cool, stopping heating; naturally cooling the silicon to room temperature and taking the solid silicon out; crushing the silicon at room temperature, adding mixed acidic solution and placing the solution in a ventilated cabinet to stand the solution for 12 hours; and separating the etched and crushed silicon grains from the acidic solution, soaking the silicon grains in water, washing the silicon grains till the silicon grains are neutral, filtering out the silicon grains and drying the silicon grains to obtain the finish product of high-purity silicon. Compared with the traditional oriented condensation and zone-melting, the method greatly improves the fractional condensation efficiency of the impurities in a condensation process, greatly reduces the purification process and improves the extraction yield of the pure material.