Objective To assess the association between serum 25-hydroxyvitamin D[25 (OH)D] levels at birth and bronchopulmonary dysplasia (BPD) in preterm infants. Methods This study recruited preterm infants with gestational age of below 34 weeks who were born between January 2014 and December 2016. These preterm infants were classified into two groups:BPD and control. The association between serum 25 (OH)D levels at birth and BPD was analyzed. Results Serum 25 (OH)D levels in the BPD group was significantly lower than those in the control group[ (37±17 nmol/L vs 47±20 nmol/L; P < 0.05), and the rate of vitamin D deficiency was significantly higher than those in the control group (90.2% vs 74.0%; P < 0.05). The level of serum 25 (OH)D was negatively correlated with the incidence of BPD (r=-0.201, P=0.001). Conclusions Vitamin D deficiency at birth may be associated with BPD in preterm infants, but need to be further studied by multivariate analysis.