Objective To study the expression of hypoxia-induced mitogenic factor (HIMF) in mouse bronchopulmonary dysplasia ( BPD) model and its significance. Methods Thirty-two Kunming neonatal mice were randomly divided into normoxia exposure group (21% 02,n=16) and hyperoxia exposure group (85% O2,n=16). After exposure for 7, 14, 21 and 28 days, HE staining was applied to observe the morphological changes of lung tissues. The mRNA and protein levels of HIMF were detected by real-time reverse transcription-polymerase chain reaction ( RT-PCR) and Western blotting, respectively. Results In normoxia exposure group, the alveoli was gradually mature and well-distributed, with thin interstitial tissue. However, in hyperoxia exposure group, the increased septa] wall thickness and alveolar fusion were observed, and the radical alveolar count was decreased by 31.1%-65.3%. As compared with normoxia exposure group, the mRNA and protein levels of HIMF were enhanced by 2.435-2.528 times (P<0.05) and 2.45-5.42 times (P<0.05) at the 7th, 14th and 21st day after exposure, but decreased by 52. 81 % (P<0. 05) and 74. 60% at the 28th day after exposure. Conclusion The mouse BPD model was successfully established, and HIMF may participate in the pathogenesis of BPD.