The invention discloses a traditional Chinese medicine for treating hyperthyroidism. The traditional Chinese medicine is prepared from the following medicinal materials in weight ratio: 10g of radix gentianae, 10g of golden cypresses, 10g of raw rhizoma arisaematis, 25g of selfheal, 25g of airpotato yam rhizome, 25g of raw oyster shells, 5g of schisandra chinensis, 15g of cortex moutan, 15g of oriental blechnum leaves, 15g of rhizoma anemarrhenae, 8g of radix bupleuri, 20g of tortoise-plastron glue, 8g of dracocephalum heterophyllum benth and 5g of rodgersia aesculifolia. A preparation method of the traditional Chinese medicine comprises the steps of weighting the medicinal materials, placing the medicinal materials into a vessel, adding 8 times of water to decoct for 1.5h, and filtering; adding 6 times of water into filter residues to decoct for 1h, and filtering; merging the filtrates, concentrating, drying and encapsulating. Clinical experiments prove that the traditional Chinese medicine is capable of achieving the remarkable effect of effectively treating hyperthyroidism through selecting the proper medicinal materials and the ratio thereof, and is safe and free of toxic or side effect.