ObjectiveTo study the ideal Kasai portoenterostomy (KPE) time for preterm infants with biliary atresia (BA) through evaluation of the postoperative effects.MethodsRetrospectively, 34 preterm infants with BA from 2012 to 2016 were recruited in the present study. The following three groups were established according to their chronological and corrected age at the time of KPE operation: chronological age90days, chronological age>90days and corrected age90days, and corrected age>90days. For chronological age90days at operation, patients were further divided into another three groups: chronological age60days, chronological age>60days and corrected age60days, and corrected age>60days. Postoperative effects were then followed up and recorded.ResultsFirst, of those patients divided according to 90-day chronological and corrected age, postoperative total bilirubin levels (TBL), direct bilirubin levels (DBL), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) of the group whose chronological age was 90days were lower than the levels of the group whose chronological age was >90days and corrected age90days (P=0.0472, P=0.0358, P=0.0083, and P=0.0491), and the group whose corrected age was >90 days (P=0.0383, P=0.0392, P=0.0043, and P=0.0107). Second, for those patients whose chronological age was 90 days, the group whose corrected age was >60 days showed a higher ALT level than the other two groups with chronological age60 days (P=0.0472) and chronological age>60 days and corrected age60 days (P=0.0258).ConclusionAccording to the present study, the ideal KPE time for preterm BA infants should meet two conditions: chronological age90days and corrected age60days. The groups with a chronological age60days, and chronological age>60days and corrected age60days show similar postoperative effects.