Undetermined blood group and unknown blood group are defined differently. Undetermined blood group means that the patient has been tested for blood group but the exact blood group has not been determined; unknown blood group means that the patient has not been tested for blood group and therefore the blood group is unknown. Blood type is the type of surface antigen in the components of blood, according to different antigen types can be divided into different blood types, mainly including ABO blood group system and Rh blood group system. Among them, Rh blood type is very rare, among Han Chinese, Rh blood type positive people account for about 99%, Rh blood type negative people account for only 1%, so the blood of Rh-negative people is also known as panda blood. The process of blood type testing involves taking the patient’s venous blood, then testing the blood for antigens on the surface of the red blood cells through a cell agglutination test, and then testing the plasma for antibodies to determine the blood type. If the antigen on the surface of the red blood cells is type A, and the antibody in the plasma is type B, then the blood type is A. By analogy, there are four ABO blood types: A, B, AB and O. In the blood transfusion, blood donation, as well as to do pre-surgical preparation, should be carried out blood type testing, to avoid blood type mismatch and hemolytic reaction, endangering the lives of patients. Before blood transfusion, medical workers need to check three times and seven times to confirm that the blood type of the transfusion recipient and the transfusion recipient are the same, otherwise it will lead to serious medical errors. Blood group testing is of great significance to clinical blood transfusion. Patients should go to regular hospitals or testing centers to clarify their blood groups to avoid accidents.