Objective To investigate the effect of chorioamnionitis on physical and neurological development in infancy of premature infants with gestational age less than 34 weeks. Methods A total of 41 premature infants with exposure to chorioamnionitis (group A) and 37 premature infants without exposure to chorioamnionitis (group B) of gestational age less than 34 weeks followed up for 12 months after discharge from Qingdao Women and Children's Hospital were enrolled in this study.33 mature healthy infants (group C) were randomly selected from the department of child healthcare.Differences of physical growth indexes,mental development index(MDI),motor development index(PDI)and neural motor development in infancy of the three groups were compared. Results 1)The weight and length development of group A and group B lagged behind those of group C at corrected age of 6 month (P＜0.05).The length development of group B lagged behind that of group C at corrected age of 12 months (P＜0.05).2)The MDI,PDI in group A were lower than those in group B and group C at corrected age of 6 month (P＜0.05);There was no significant difference in MDI,PDI among three groups at corrected age of 12 month(P＞0.05).The incidence of abnormal results in the 20 items of neuromotor assessment in group A and group B was higher than that in group C at corrected age of 6 months and 12 months (P＜0.05). Conclusion Premature infants with gestational age less than 34 weeks exposed to chorioamnionitis are more likely to develop physical and mental retardation in infancy.