Negative blood refers to a blood type in the human body, i.e. Rh-negative blood. Negative blood refers to Rh-negative blood. Because there are many human blood group systems, two are widely used in clinical practice, one is the ABO blood group system and the other is the Rh blood group system. The average person understands the ABO blood group system, while most people are unfamiliar with the Rh blood group system. The Rh blood group system was first discovered in the red blood cell membranes of Indian rhesus monkeys. In humans, the Rh blood system is categorized into two groups based on whether or not the red blood cell membranes contain the D antigen; those containing the D antigen are RH-positive, and those without the D antigen are RH-negative. Negative blood types are those that do not have D antigen on their red cell membranes. In the Chinese Han population, Rh-positives make up the majority, while Rh-negatives are very rare, and Rh-negative blood is often clinically deficient in blood supply.