If you go to the hospital for a blood type test, there is usually a description of one of A, B, AB, O, and one of RH positive or RH negative on the test report, which is the most comprehensive expression of a person’s blood type. In clinical practice, there are two clinically significant and widely used blood group systems, one is the ABO blood group system, and the other is the RH blood group system, which includes A, B, AB and O blood types, of which a person can only be one. In addition to the ABO blood type, there is also the RH blood type system, RH blood type system most people are relatively unfamiliar, but the RH blood type system is very important, RH blood type system is divided into RH positive and RH negative two, in our country most people are RH positive, RH negative people are very few.