Objective To investigate the role of Vitamin D (VitD) on amelioration of chorioamnionitis-induced alveolarization arrest and possible mechanisms. Methods A neonatal rat bronchopulmonary dysplasia (BPD) model was constructed by intra-amniotic injection of lipopolysaccharides (LPS) in pregnant rats. Rats were randomly assigned to the Saline group, LPS+Saline group，LPS+VitD (L) group, and LPS+VitD (H) group. Neonatal rats in the LPS+VitD (L) group and the LPS+VitD (H) group were intraperitoneally injected with 0.5 and 3 ng/g 1, 25(OH)2D3 respectively once a day for 7 d. Meanwhile, neonatal rats in the Saline group and the LPS+Saline group were intraperitoneally injected with the same volume of normal saline. The pulmonary tissues of neonatal rats were harvested 1, 3, and 7 d after the final injection and were stained by H-E staining for observing pathological changes. The mRNA expressions of IL-1β and IFN-γ  were detected using real-time PCR. Results Different concentrations of VitD could improve the birth rate of neonatal rats (P=0.003). The LPS+VitD (L) group and the LPS+VitD (H) group had significantly higher alveolar counts (P=0.001, P=0.000), remarkably decreased mean liner intercept (P=0.000), and significantly decreased mRNA expressions of IL-1β and IFN-γ as compared with the LPS+Saline group 7 d after birth (P=0.000). Conclusion Administration of VitD can significantly decrease the expressions of IL-1β and IFN-γ in lungs of neonatal rats and alleviate the pathological changes of BPD.