Objective To explore the relationship between expression of matrix metalloprotein-9 (MMP-9) and tissue inhibitor of metalloproteinases 1 ( TIMP-1) in premature infants with FIRS and bronchopulmonary dysplasia. Methods This study was designed with clinical and animal experiments. Clinical experiments: From May 2018 to December 2019, 118 preterm samples were obtained and divided into control group and experimental group, to observe inflammatory indicators (IL-6, MMP-9, TIMP-1 and M/ T ratio) and pathological tissue infiltration by inflammatory cells and analyze the relationship between inflammatory indicators of the groups. Animal experiments: Establish the pregnant mice and randomly divided them into three groups, lipopolysaccharide group (LPS, n= 10), retinoic acid group (RA, n= 10) and normal saline group (NS, n= 10). The inflammatory indexes of lung tissues and inflammatory cell infiltration in placental pathological tissues in the three groups were assessed, and the relationship between the inflammatory indexes of the three groups was analyzed. Results The expression levels of IL-6, MMP-9, TIMP-1 and the M/ T ratio in cord blood of premature infants in the FIRS group of different gestational ages were significantly higher than those in the control group (P<0. 01). The incidence of BPD in the FIRS group was higher than that in the control group at the same gestational age. Animal experiments: The expression levels of MMP-9 and TIMP-1 and the M/ T ratio in newborn (fetal) rats of different FIRS age groups were significantly higher than those of the control group at the same age (P<0. 01). After RA treatment, the inflammatory index was higher than that in the control group at the same age (P<0. 01), but lower than that in the FIRS group at the same age (P<0. 01). IL-6 was positively correlated with MMP-9, TIMP-1 and the M/ T ratio in mice lung tissue. Conclusions FIRS regulates MMP-9, TIMP-1 levels and the M/ T ratio, mediates BPD and the application of an MMP-9 inhibitor plays a protective role in the process of lung injury, which provides a potential drug target for clinical treatment.