Objective To explore the relation of serum activin A (ACT A) in neonatal brain damage and its clinical significance in neonates with hyperbilirubinemia. Methods Serum levels of ACT A were measured using ELISA in 61 term neonates with hyperbilirubinemia and 25 normal term neonates.Meanwhile,The hyperbilirubinemia group was classified into three subgroups based on serum total serum bilirubin(TSB) levels in mild (221~256 μmol/L),moderate (257~342 μmol/L)and severe (>342 μmol/L).Serum TSB levels in the 25 normal neonates were less than 85 μmol/L (control group). Results ACT A levels in the mild,moderate and severe hyperbilirubinemia groups[(3.68±0.62),(4.32±0.53) and (5.12±0.71) μg/L,respectively] were obviously higher than those in the control group(P<0.05).There were significant differences among the three hyperbilirubinemia sub groups in serum ACT A levels (P<0.05).And it increased with the increase of bilirubin.Serum ACT A levels were positively correlated to the bilirubin(r=0.82,P<0.01). Conclusion Activin A levels is associated with bilurubin-induced brain damage and correlated to the level of serum bilirubin.