Objective: To study the correlation of IgG anti-A/B titer score and the severity of hemolytic disease of newborn. Methods: The red blood cell count, hemoglobin and hematocrit value of 27 newborn with hemolytic disease and the IgG anti-A/B titer and titer score of their mother were measured and their correlations were analyzed. Results: With the increase in IgG anti-A/B titer and titer score of mother, the red blood cell count, hemoglobin and hematocrit values of newborn with hemolytic disease decreased. At the same IgG anti-A/B titer, the higher the titer score, the lower the red blood count, hemoglobin and hematocrit value were. Conclusions: According to the correlation analysis, the titer score is more closely related to the severity of hemolytic disease of newborn. For hemoglobin, the correlation coefficient was -0.966. The IgG anti-A/B titer score was of more clinical significance in predicting the severity of hemolytic disease in newborn.