The invention discloses a method of purifying silicon metal by coating with an aluminum film, which comprises the following steps of deoiling and washing the silicon metal; adding the silicon metal in aluminum hydroxide colloid for uniform mixing and drying; heating in the water gas atmosphere and heat insulating for twice and then cooling to the room temperature; and finally soaking the silicon metal in mixed solution of hydrochloric acid and hydrofluoric acid and cleaning with deionized water to obtain advanced silicon metal with the purity of 4-5N. The method utilizes the aluminum gettering for preliminary gettering treatment for the impurities in the silicon metal, the process is simple, the cost is greatly reduced, and the relatively pure silicon material can be obtained as the silicon material of a solar battery or further purified raw material can be obtained.