Objective To explore the incidence and influencing factors of extrauterine growth retardation(EUGR) in premature infants with gestational age ≤ 34 weeks old, in order to provide reference for facilitating the healthy growth and development of preterm infants. Methods The clinical data of 315 premature infants whose gestational age was ≤ 34 weeks and were delivered in Nanjing Maternal and Child Health Hospital from January 2016 to January 2018 were retrospectively collected and analyzed.According to whether infants had EUGR or not, infants were divided into developmental retardation group(retardation group) and typical development group(normal group).The influencing factors of EUGR in preterm infants were analyzed by multivariate Logistic regression analysis. Results The proportions of birth weight ＜1 500 g, gestational age＜28 weeks, head circumference at birth ≤33 cm, duration of body mass decline ＞6 d, maternal gestational hypertension, minimum body weight and body mass at discharge indevelopmental retardation group were significantly higher than those in typical development group(P<0.05).And the first breastfeeding time, time for achieving enteral feeding, intravenous nutrition duration, duration of minimal feeding, the proportions of sepsis, respiratory distress syndrome and feeding intolerance were significantly higher than those in typical development group(P<0.05).Multivariate Logistic regression analysis showed that birth weight＜1 500 g(OR=1.719, 95%CI:1.115—2.652), gestational age ＜28 weeks(OR=1.587, 95%CI:1.052—2.396) and time for achieving enteral feeding≥17 d(OR=1.835, 95%CI:1.144—2.943) were risk factors of EUGR in premature infants(P<0.05). Conclusions The influencing factors of EUGR in premature infants with gestational age is ≤34 weeks include birth weight, gestational age and time for achieving enteral feeding.And nutritional support should be taken as soon as possible to reduce EUGR risk.