Objective To study the coagulation function of premature infants at birth and the associated risk factors.Method From January 2014 to January 2018,a prospective study was conducted on preterm infants born in obstetrics department of our hospital.According to the gestational age,these infants are assigned into early preterm group,moderate preterm group and late preterm group.The prothrombin time (PT),activated partial thromboplastin time (APTF),fibrinogen (FIB) and thrombin time (TT) were measured using automatic coagulation analyzer.The possible risk factors affecting the coagulation function in each group were analyzed.Result A total of 795 preterm infants were studied including 93 in the early preterm group,151 in the moderate preterm group and 551 in the late preterm group.In the early preterm group,infants with premature rupture of membranes (PROM) had increased FIB,shortened TT,and infants with severe asphyxia had prolonged PT,and the differences were statistically significant (P ＜ 0.05).In the moderate preterm group,infants with PROM had significantly prolonged APTT (P ＜ 0.05).In the late preterm group,PT and TT were prolonged and FIB was decreased in male infants.Infants with PROM have increased FIB;PT was prolonged among infants with severe asphyxia (P ＜ 0.05).Multivariate linear regression analysis showed that neonatal asphyxia,weight and gender were the main factors affecting PT (P ＜ 0.05),gestational age was the main risk factor affecting APTT (P ＜ 0.05),PROM,gestational age,weight and gender were the main factors affecting FIB (P ＜ 0.05),and neonatal asphyxia was the main factor affecting TT (P ＜ 0.05).Conclusion The coagulation function of premature infants is affected by many factors including gender,gestational age,weight,asphyxia,PROM,and maternal complications.Coagulation function should be monitored in preterm infants with severe asphyxia.