Hemolytic transfusion reaction is a very serious complication, divided into acute hemolytic transfusion reaction, delayed hemolytic transfusion reaction, acute hemolytic transfusion reaction is a few minutes after the beginning of the transfusion will cause hemolytic symptoms immediately, the time comes quickly, the symptoms come to a more typical, can be quickly found, this disease rescue time is also relatively fast, but the delayed hemolytic transfusion reaction time cycle is longer, easier to be covered up by the original disease, because weeks, days or even months later to find hemolysis, this disease is easy to be covered up. However, delayed hemolytic transfusion reaction has a longer time period and is more easily masked by the primary disease because hemolysis is not detected until weeks, days, or even months later. The occurrence of delayed hemolytic reaction will also be more harmful. Generally, delayed hemolytic transfusion reaction can be detected within 1-2 weeks, but delayed hemolytic reaction after bone marrow transplantation may also occur in 1-3 months. It is mainly due to the fact that repeated transfusion of blood, or pregnant women who have had a previous transfusion, will stimulate the body to produce a kind of antibody, which is in a small amount in a short period of time, and is undetectable and unknown to its If the same blood product is encountered again, which is equivalent to the same red blood cell antigen and stimulated again, a lot of antibodies will be produced suddenly, which will produce antigen-antibody reaction with the original red blood cell antigen, resulting in a strong hemolytic reaction. This situation usually occurs in pregnant women who have had many repeated blood transfusions, so clinically it is more concerned about delayed hemolytic transfusion reaction, and it is also a hemolytic reaction that is easier to ignore.