Aim To investigate the effect of D-galactose on rat pulmonary fibrosis and matrix metalloproteinases (MMP-2) expression and the contents of the hyaluronic acid (HA), Laminin (LN), Collagen type Ⅲ (COL3) in the lung tissue of rat, and to analyze the correlation between MMP-2 and HA, LN, COL3. Methods The SD rats were randomly divided into two groups:normal group and D-galactose group. Morphological changes of lung tissue were observed by HE staining in two groups of rats. The mRNA expression of MMP-2 in the lung tissue in each group was detected by real-time fluorescent quantitative PCR (qRT-PCR). The immunohistochemistry (IHC) and Western blot method were used to detect MMP-2 protein expression in lung tissue. The enzyme-linked immunosorbent assay (ELISA) was used to detect the content of HA, LN and COL3 in rat lung tissue, and the correlation between them was analysed. ResultsHE staining showed that the lung tissue of D-galactose group had obvious fibrosis changes. The mRNA and protein expression levels of MMP-2 in D- galactose induced group were higher than normal group(P＜0.05), and the contents of COL3 and laminin (LN) were higher than normal rats, but the content of hyaluronic acid (HA) was lower than the normal groups (P＜0.05). Correlation analysis results showed that the expression level of MMP-2 in the rats lung tissue was positively correlated with COL3 and LN, but negatively correlated with HA (P＜0.05). Conclusion D-galactose can cause lung fibrosis changes in aged rats, and could increase the expression level of MMP-2 and the content of COL3 and LN, and decrease the content of HA in the rats lung tissue, and there is a correlation between MMP-2 and COL3, LN, and HA which may provide other diagnostic basis for the detection of pulmonary fibrosis.