Disclosed is a system for refining UMG Si including a vacuum chamber, a cold crucible disposed within the vacuum chamber, a device disposed within the vacuum chamber to supply Si to the cold crucible, a steam plasma torch disposed above the cold crucible to apply steam plasma formed by introducing a reactive gas into plasma flame by an inert gas to the Si supplied to the cold crucible, and an impurity collector disposed above the cold crucible within the vacuum chamber to collect impurity gas generated in the cold crucible and discharge the collected impurity gas to the outside of the vacuum chamber.