Objective　To analyze the relationship between serum 25(OH)D level and lung diseases in premature infants. Methods　The clinical data and the results of serum 25 (OH) D were collected in the preterm infants admitted to NICU from January 2015 to December 2016. According to the average level of serum 25 (OH) D, the premature infants were divided into low vitamin D group and high vitamin D group, and the differences of lung diseases between two groups were compared. Results　A total of 115 premature infants were enrolled. The mean gestational age was (29.9±1.9) weeks, and the mean serum 25(OH)D level was (37.1±16.6) nmol/L. The rates of vitamin D deficiency [25(OH)D<50 nmol/L], vitamin D insufficient [25(OH)D 50-75 nmol/L] , and normal [25(OH)D≥75 nmol/L] were 71.3%, 17.4%, and 11.3%, respectively. The persistent positive airway pressure, oxygen therapy time, the incidences of neonatal respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD), and hospitalization days in the low vitamin D group were significantly higher than those in the high vitamin D group (P all<0.05). Conclusions　Preterm infants with low vitamin D levels may increase the incidences of RDS and BPD, and prolong the length of hospitalization.