Rh-negative O blood type, expresses two blood group systems. The first is the RH system and the ABO blood group system, which are currently the two most important blood group systems on red blood cells.The ABO blood group system was first discovered and is typed according to whether the red blood cells express the A or B antigen. If the A antigen is expressed, it is called type A, if the B antigen is expressed, it is called type B, and if both AB antigens are expressed, it is called type AB. The Rh blood group system is also named according to the distribution of Rh antigens on red blood cells, and there are five types of Rh antigens, including D, C, c, E, and e. The D antigen is the current routine test, and if there is no D antigen on red blood cells, it is called Rh negative. If there is a D antigen of RH on the red blood cells, it is called Rh positive. If the red blood cells lack both the A and B antigens of the ABO blood group system and there is no D antigen of the Rh blood group system, it is called Rh-negative O blood group.