Method for preparing solar grade polysilicon

The invention relates to a method to prepare solar-grade polycrystalline silicon. Wherein, using metallurgical-grade silicon as material, breaking and grinding to obtain the silicon power with grain size more than 50 orders; dipping the silicon powder into 1-6mol/L hydrochloric acid, 0.5-6mol/L nitric acid and 1-5mol/L hydrofluoric acid, respectively; then, adding the material into vacuum furnace for vacuum refining treatment with two stages of the vacuum oxidation refining on condition of furnace vacuum degree 90000-1000Pa and 1430-1500Deg and the vacuum distillation refining and degassing on condition of furnace vacuum degree 10-2~10-5Pa and same temperature; finally, directional solidifying and cutting heads to obtain the product. This product has purity more than 99.9999% and specific resistance more than 0.4a©incm, and can meet industrial request.