The present invention relates to a method for preparing a polysilicon rod using a metallic core means, comprising: installing a core means in an inner space of a deposition reactor used for preparing a silicon rod, wherein the core means (C) is constituted by forming one or a plurality of separation layer(s) on the surface of a metallic core element and is connected to an electrode means (E), heating the core means (C) by supplying electricity through the electrode means (E), and supplying a reaction gas (Gf) into the inner space (Ri) for silicon deposition, thereby forming a deposition output in an outward direction on the surface of the core means (C). According to the present invention, the deposition output (D) and the core means (C) can be separated easily from the silicon rod output obtained by the process of silicon deposition, and the contamination of the deposition output caused by impurities of the metallic core element (Ca) can be minimized, thereby a high-purity silicon can be prepared in a more economic and convenient way.