Infectious anemia is caused by various bacteria or viruses that invade the human respiratory tract and cause infection, resulting in increased destruction of red blood cells in the body or damage to the hematopoietic function of the bone marrow, and possibly the inability of iron to be used for blood production can lead to anemia, i.e. infectious anemia. Some chronic infections tend to cause infectious anemia. We will find that the patient’s anemia will be moderate anemia in the usual examination, but usually there will be positive cellular anemia and also small cellular anemia, at this time we have to exclude whether there is iron deficiency anemia and do relevant examination to identify it.