Abstract: Objective: To study the role of β-glucuronidase(β-GD) in breast-milk jaundice in neonates and its diagnostic vaule.Methods: The study was conducted on 60 neonates with breast-milk jaundic(study group) and 70 healthy newborns(control group).The β-GD activity and the serum total bilirubin concentration was estimated in the breast milk and the infants' feces at day 7,14,21 and day 28.The positive rates of β-GD activity in the breast-milk jaundic were determined at the same time points.Results: The difference of β-GD activities in the study group and the control group had statistical significance(P<0.001).The infant fecal β-GD activities at each time point was obviously different between the two groups(P<0.001).The serum total bilirubin levels had positive correlation to the β-GD activities both in breast milk and infant faces in the study group and the correlation coefficients were 0.785 and 0.753,respectively(P<0.01).The positive rates of milk β-GD in infants with breast milk jaundice and healthy newbrons were 80.0% and 7.1% respectively.The difference was significant(P<0.005).Its sensitivity,specificity,positive predicting value,negative predicting value and correct diagnostic rate were 80.0%,92.9%,90.6%,84.4%,and 86.9%,respectively.The positive rates of fecal β-GD measurement in babies with breast-milk jaundice and healthy newbrons were 78.3% and 5.7% respectively.The difference was significant(P<0.005).Its sensitivity,specificity,positive predicting value,negative predicting value and correct diagnostic rate were 78.3%,94.3%,92.2%,83.5% and 86.9%,respectively.Conclusions: β-GD activity plays an important role in breast-milk jaundice in neonates.The measurement of β-GD in breast-milk and infants'feces is of value for diagnosis of breast-milk jaundice.