The ABO blood group is the most important system in clinical transfusion medicine. Previous studies on the genetic base of the common ABO group and some rare ABO subgroups have suggested that the molecular genetic background of the ABO gene in the Chinese population has specific character. In this study, we carried out a molecular genetic analysis of a family with an individual diagnosed as Ael subgroup by serological tests. A novel allele was identified in our A subgroup cases.