Abstract: The objective of this study was to observe the oxidative damage of lung tissue induced by formaldehyde in mice. The experimental mice were administrated with multiple doses of liquid formaldehyde with different concentrations by intratracheal medication. Subsequently, the mice were sacrificed, and their lung tissue were collected to determine the pulmonary surfactant-associated protein A （SP-A） content, superoxide dismutase （SOD） activity and malondialdehyde （MDA） content. Furthermore, the lung tissue sections were prepared, and the pathological changes were observed by means of light microscopy. The results showed that the high and low dosage groups had significantly lower SP-A content and SOD activity compared to the saline solution control group （P〈0.05） and had significantly higher MDA content （P〈0.05）; the increased number of stromal cells in pulmonary alveoli and inflammatory cells were observed, and the inflammatory cell infiltration were found. The combined data suggest that formaldehyde is able to cause oxidative damage of lung tissue in mice.