B-positive means that a person’s blood type is B in the ABO blood group system and Rh-positive in the Rh blood group system. Because there are various human blood group systems, the ABO blood group system and the Rh blood group system are widely used in clinical practice. the ABO blood group system is clinically divided into A blood type, B blood type, AB blood type and O blood type. the Rh blood group system is clinically divided into two categories: Rh positive and Rh negative. the vast majority of the Han Chinese population in China is Rh positive, and there are very few Rh negative people. the Rh negative blood can only receive Rh-negative blood, and if Rh-positive blood is imported, a serious hemolytic reaction will occur. However, Rh-positive blood can receive both Rh-positive and Rh-negative blood.