NOVELTY - A polycrystalline silicon purifying method involves coating a layer of silicon nitride on an inner surface of a crucible. The crucible is preheated. Heating of the crucible is stopped, and liquid silicon is poured into the crucible. Mixed gas is blowed into the liquid silicon in a molten state. The liquid silicon is rapidly performed with directional solidification. The blowing of gas is stopped. The liquid silicon not solidified on the center part of a silicon ingot, is poured out. Flaw-pieces are removed for obtaining high purity polycrystalline silicon.    USE - Method for purifying polycrystalline silicon that is utilized in a solar photovoltaic battery.    ADVANTAGE - The method enables purifying the polycrystalline silicon using a simple and easy process in a cost effective manner, and improving development of the polycrystalline silicon material and a solar photovoltaic battery.    DETAILED DESCRIPTION - A polycrystalline silicon purifying method involves coating a layer of silicon nitride on an inner surface of a crucible, where thickness of the coating is 0.1-0.49 mm. The crucible is preheated at temperature of 800-1200 degrees C for 6-10 hours. Heating of the crucible is stopped, and liquid silicon having temperature of greater than 1600 degrees C is poured into the crucible. Components and volume ratio of a mixed gas are selected according to purity of the liquid silicon. The mixed gas is blowed into the liquid silicon in a molten state from a bottom part of the crucible, and pressure and flow rate of the blown gas are controlled. The liquid silicon is rapidly performed with directional solidification from a bottom part and a surrounding part toward a center part. The blowing of gas is stopped after a certain time. The liquid silicon not solidified on the center part of a silicon ingot, is poured out. Flaw-pieces of the surrounding part, a head part, a tail part, and central hollow sphere of the silicon ingot are removed for obtaining high purity polycrystalline silicon.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a crucible.