The invention relates to a process for preparing high-purity alumina polycrystal from suspended graphite via a cold crucible. The process comprises the following steps: filling the cold crucible with high-purity alumina raw powder and compacting the high-purity alumina raw powder to allow the height of the compacted raw powder to be located between the upper edge height and the lower edge height of high-frequency induction coils; then putting graphite flakes with high purity of more than 99.99% on a spread backing material and uniformly covering the graphite flakes with a layer of uncompacted raw powder with a height of 1 cm; starting a crucible water-cooling system, turning on the power source of the induction coils and carrying out induction heating; allowing the graphite flakes to be rapidly heated to 3000 DEG C or above and rapidly melting nearby raw powder to form an alumina molten pool after complete melting of the raw powder, thereby allowing the graphite flakes to float above the molten pool and contact with air; allowing the crucible to begin to descend, continuing feeding of the raw powder into the cold crucible and allowing the graphite flakes to always float on the top of the molten pool, to continuously contact with air and to be oxidized into carbon dioxide gas until the graphite flakes eventually vanish; and finally, completing production of the high-purity alumina polycrystal.