The invention provides a drug for treating radiation injury and a method for preparing the same, and belongs to the field of traditional Chinese medicine preparation process. The traditional Chinese medicines are used as raw materials to prepare the drug through extraction of a formulation. The drug is characterized in that the drug consists of four medicinal materials in portion by weight: 5 to 15 portions of integripetal rhodiola herb, 15 to 25 portions of astragalus root, 5 to 15 portions of acanthopanax root extract and 80 to 100 portions of sea backthern. The preparation method comprises that: the astragalus root and the sea backthern are mixed, are decocted with water for two times, and are filtered; the filtrate is combined and is condensed to extract with relative density of between 1.28 and 1.30 (80 DEG C); and the extract, the acanthopanax root extract and pulverized integripetal rhodiola herb fine powder are mixed and evenly stirred, are dried at temperature of 60 DEG C, are pulverized, are filtered by a 80-mesh sieve, and are pelletized into particles; and the particles are dried at temperature of less than 80 DEG C, and are capsulated into a No. 0 capsule to obtain the drug. The clinical test and experimental research show that the drug has the function of treating the radiation injury, and has no obvious adverse reaction, abundant sources of the raw materials, and low production cost.