Abstract: The effect of total flavonoids of astragalus （TFA）on the immunity o dogs receiving intraoperative radiation（IORT） was observed, the result showed IORT reduced the lymphocytic transformation rate,and the germ-destroying ability of neutrophils ,while TFA has protective effect against the above-mentioned injury of immunity system by IORT. The mechanism maybe related with TFAs properties such as anti-oxidation and scavenging free radicals,which can protect immunal cells from lipidperoxidation injury.Meanwhile,TFA can also influence the energeticmetabolism of immune cells and promote lymphocytic mitosis.