AB positive blood type means that a person’s blood type is AB in the ABO blood group system and Rh positive in the Rh blood group system. Because there are dozens of human blood group systems, only two are widely used in clinical practice, one is the ABO blood group system and the other is the Rh blood group system. the ABO blood group system classifies human blood types into four categories, namely A blood type, B blood type, O blood type and AB blood type. the Rh blood group system classifies human blood types into two types, one is Rh-positive blood and the other is Rh-negative. Those with D antigen on the blood red blood cell membrane are Rh positive blood, and those without D antigen are Rh negative blood. Therefore, AB positive blood type means that in ABO blood system is AB blood type, and Rh blood system is Rh positive blood.