A method for preparing a polysilicon rod using a metallic core means, including: installing a core means in an inner space of a deposition reactor used for preparing a silicon rod, the core means being constituted by forming at least one separation layer on the surface of a metallic core element and being connected to an electrode means, heating the core means by supplying electricity through the electrode means, and supplying a reaction gas into the inner space for silicon deposition, thereby forming a deposition output in an outward direction on the surface of the core means. The deposition output and the core means 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 can be minimized, thereby a high-purity silicon can be prepared more economically and conveniently.