Astragaloside IV(ASI),a saponin-like compound,one of the major important secondary metabolites isolated from Astragalus Membranaceus,has been shown has many biological properties,such as antioxidant,antiaging,antiviral,inhibiting intracellular calcium overload and reducing the cardiac ischemia reperfusion injury in rat model by scavenging free radical species.To estimate the potential radioprotective ability of ASI against radiation-induced acute lung damages in mice and provide experimental evidence for cancer radiotherapy in the chest.The Kun-Ming mice were randomly divided into four groups:normal control group(did not receive any treatment,CK),irradiation on- Astragaloside IV (ASI), a saponin-like compound, one of the major important secondary metabolites isolated from Astragalus Membranaceus, has been shown to have many biological properties, such as antioxidant, antiaging, antiviral, inhibiting intracellular calcium overload and reducing the cardiac ischemia reperfusion injury in rat model by scavenging free radical species. To estimate the potential radioprotective ability of ASI against radiation-induced acute lung damages in mice and provide experimental evidence for cancer radiotherapy in the chest. Kun-Ming mice were randomly divided into four groups: normal control group (did not receive any treatment, CK), irradiation on-