Commonly used methods of blood typing are the slide method and the test tube method. The principle of the slide method and test tube method to identify the blood type is to use the known antiserum to fuse with the subject’s blood to observe whether there is any agglutination reaction occurs, that is, the subject’s blood is dropped on the slide at two places (or the subject’s blood is taken into two test tubes), and then take a copy of serum containing anti-A antibody and a copy of serum containing anti-B antibody to be dropped into the two copies of the blood respectively. Observe the blood of the two subjects to see if any agglutination reaction occurs to analyze the blood type. If agglutination occurs in the blood with the anti-A antibody serum and not in the blood with the anti-B antibody serum, then the blood type is A. Conversely, the blood type is B. If neither of the two serums agglutinate, then the blood type is B. The blood type is B. If no agglutination occurs with both, it is type O. If agglutination occurs with both, it is type AB.