Objective:To explore the impact of postnatal long-term corticosteroids use on early lung development and find the relation between glucocorticoids and insulin-like growth factor binding protein 2(IGFBP-2). Methods:Total 48 neonatal rats were randomly divided into 3 groups:control group (nebulized saline),budesonide group (nebulized budesonide) and dexamethasone group (intraperitoneal injection of dexamethasone). Treatment began at 5 day of age and continued for 1 to 2 week period. At the end of treatment,body weight and lung index were investigated. Alveolar counts,alveolar septum thickness and alveolar space as morphologic markers were used to evaluate alveolar development. The expression of IGFBP-2 was detected by Western Blot. Results:①There was no significant difference in body weight between budesonide group and control group (P > 0.05). Body weight was significantly decreased in dexamethasone group compared with control group after 14 days exposure(P < 0.01). There was significant difference in lung index between budesonide group and control group(P < 0.01),but there was no statistical difference in lung index between dexamethasone group and control group after 14 days treatment(P > 0.05). ② The total number of alveoli,thickness of the alveolar wall were dramatically reduced and alveolar space increased in budesonide and dexamethasone treated groups when compared with control(P < 0.01,P < 0.05 respectively). No significant differences about the three morphologic markers were seen between budesonide group and dexamethasone group. ③ The expression of IGFBP-2 in lung tissue of budesonide and dexamethasone groups significantly increased compared with control group detected by Western Blot. Conclusion:Long-term corticosteroids use affects postnatal lung alveolization. The overexpression of IGFBP-2 in lung tissue may relate to the pathological changes.