Objective:To compare the differences of hemolysis between OA and OB blood type in ABO hemolytic disease of the newborn (ABO-HDN), to study the clinical features of ABO hemolytic disease in different type.Methods:From January 2015 to June 2020, full-term ABO-HDN neonates born to blood type O mothers admitted to our hospital were enrolled in this retrospective study. The neonates were assigned into OA group and OB group. SPSS 25.0 software were used to analyze the clinical data.Results:A total of 755 cases were enrolled, including 364 cases of OA group and 391 cases of OB group. On hour-specific bilirubin nomogram, no significant differences existed in high intermediate risk zone between the two groups ( P>0.05). In the low risk zone and the low intermediate risk zone, the proportion of newborns in OA group was higher than the OB group ( P<0.05). In the high risk zone, the proportion of newborns in the OB group was higher than the OA group ( P<0.05). The age of admission of the OB group was younger than the OA group ( P<0.05). The incidences of immunoglobulin usage and blood transfusion in the OB group were higher than the OA group ( P<0.05). No significant differences existed between the two groups in Coombs? test, antibody elution test, free antibody test, platelet count, reticulocyte percentage, the onset time of jaundice, the median serum total bilirubin level, the average hemoglobin level and the incidence of anemia on admission ( P>0.05). No significant differences existed in the incidence of exchange transfusion, the duration of phototherapy and hospitalization between the two groups ( P>0.05). Conclusions:Compared with OA incompatibility, newborns with OB incompatibility have higher incidences of hyperbilirubinemia, blood transfusion and younger age of admission. However, the two groups have similar rate of exchange transfusion and phototherapy and hospitalization duration.