Abstract: 【Abstract】 Objective To study the relative factors on peri-operative status of patent ductus arteriosus (PDA) ligation and the bronchopulmonary dysplasia (BPD) in extremely preterm infants and to evaluate the safety of PDA ligation performing in the neonatal intensive care unit (NICU). Methods From May 2015 to April 2018, 44 cases were admitted with birth weight < 1,500 g and gestational age between 28 to 31+6 weeks and undergoing PDA ligation in the NICU of Bayi Children's Hospital. The infants were divided as BPD group (29 cases) and none BPD group (15 cases) according to their discharge diagnosis. The clinical data were analyzed on gestational age, birth weight, onset date and weight at surgery, ibuprofentherapy, incidence of RDS, perioperative ventilatory parameters and vital signs, duration of ventilation, total days of oxygen therapy, and surgery-related complications and hospital stays of the infants. The statistical analysis was carried out by t test, χ2 test or Fisher exact probability methods. Results The BPD group were lower(all P<0.05 )than the none BPD group in gestational age [(29.3±2.1)vs(30.7±1.6)weeks] and birth weight [(1 050±190) vs (1 220±140) g] significantly.The BPD group were longer (all P<0.05) than the none BPD group in durations of oxygen therapy[(36±14)vs(27±13)d] and the lengths of hospitalization[(73±22)vs(53±19)d] . There were no significant differences in onset date and weight at surgery, time of ibuprofen therapy , incidence of RDS, duration on ventilation. The BPD group were higher (all P<0.05) than the none BPD group in fractions of inspired oxygen before and 24 hours after surgery [0.46±0.13 vs 0.33±0.11, 0.43±0.12 vs 0.32±0.13] .There were no significant differences in mean airway pressure, temperature, pulse and blood pressure on preoperative and postoperative between two groups. Conclusions The immature degree (gestational age and birth weight) of extremely premature infants and related to the perioperative state may be an important factor to cause occurrencing BPD after PDA ligation . PDA ligation is safe and feasible to perform in the NICU.