Transfusion-associated graft-versus-host disease (TA-GVHD) is known as one of common complications of blood transfusion. The blood irradiation is generally accepted as a proven method to prevent from this disease, for the reason that it makes lymphocytes inactivated in blood products. The blood irradiation indicator provides a guarantee of proper radiation dose, thus improving the transfusion safety. Though widely used in developed countries for decades, the blood irradiation indicator is still in the initial stage in our country. In this review, the action principle, applications and applied value of the blood irradiation indicator are summarized briefly.