Objective: To investigate the regulatory role of microRNA-34a-5p on vascular endothelial growth factor (VEGF) in the course of bronchopulmonary dysplasia (BPD). Methods: Build the SD rats BPD model. 10 rats were randomly selected on postnatal days 1, 7, 14 and 21 to observe the morphological changes of rat lung tissue. Quantitative Real-time PCR (qRT-PCR) technique detection of miR-34a-5p and VEGF mRNA expression. Elisa was used to detect VEGF expression levels in lung tissues. RLE-6TN cells were divided into the miR-34a-5p-mimic group, miR-34a-5p-inhibitor group, NC group, and inhibitor-NC group. QRT-PCR technique was used to detect the expression of miR-34a-5p and VEGF mRNA levels, and Western blot was used to detect VEGF protein expression levels. Results: As the number of days increased, the lung tissues of rats in the experimental group showed pathological changes of “new BPD”. The expression levels of miR-34a-5p in experimental group were significantly higher than those in control group on day 14 and day 21, and the expression of VEGF mRNA and protein in experimental group were significantly lower than those in control group from day 14 onwards. The differences were all statistically significant (P<0.05). In the cell model, the expression of VEGF mRNA and protein levels in miR-34a-5p-mimic group decreased compared to the NC group, while the expression of VEGF mRNA and protein levels in miR-34a-5p-inhibitor group increased compared to inhibitor-NC group, and the differences were statistically significant (P<0.05). Conclusion: MiR-34a-5p may be involved in the pathogenesis of “new BPD” through the regulation of VEGF.