To investigate the protective effect of aspirin on primary cultured type II alveolar epithelial cell (AEC II), and the mechanism of its effect on anti oxidation damage. The original generation of adult rat AEC II were cultured and purified. They were divided into normal saline (NS) group, hydrogen peroxide injury group (H(2)O(2) group), and 1, 2, 3 aspirin pretreatment groups (A1-3 groups).In H(2)O(2) group, 0.5 mmol/L H(2)O(2) was added to AEC II after 40 hours of culture to reproduce a cell oxidative injury model. In NS group, only NS was added to AEC II culture. To the A1-3 groups aspirin 50, 100 and 200 μmol/L were added respectively. Cell form, cell count and cell survival rate were observed at 3 hours after H(2)O(2) was given . Immunohistochemical and polymerase chain reaction (PCR) methods were used for the determination of heme oxygenase-1 (HO-1) protein and HO-1 mRNA (20, 40, 60 hours of culture). With trypsin digestion and immune adherence method AEC II could be harvested (2.0-2.5)× , and the purity and activity were both over 90%. Compared with NS group, gaps between cells were widened in H(2)O(2) group, cell account was reduced, and the survival rate (A value) was reduced significantly (0.054 6±0.004 0 vs. 0.103 8±0.009 9, P<0.01). Compared with H(2)O(2) group, in A1-3 groups the number of adherent cells was increased, cell morphology was intact, and no obvious cell shrinkage was found. Higher survival rate (A value) was found in A1-3 groups than that of H(2)O(2) group (0.066 9±0.003 9, 0.071 0±0.006 5, 0.078 7±0.009 2 vs. 0.054 6±0.004 0, all P<0.01). Compared with NS group, HO-1 protein and HO-1 mRNA expression in AEC II after 20, 40 and 60 hours of culture reached peak level at 60 hours, and they were increased significantly in A1-3 groups [protein (A value): 1.59±0.12, 1.60±0.09, 1.61±0.08 vs. 1.25±0.11; mRNA (the ratio of Ct value: 24.31±1.74, 30.45± 2.53, 32.63±3.74 vs. 22.99±1.95, all P<0.05]. There was no significant difference in HO-1 protein expression among A1-3 groups. There are significant protective effects of aspirin against anti oxidative damage in cultured AEC II cell. As expression of HO-1 is increased in aspirin groups, it may be considered as a protective factor against anti oxidative damage in AEC II cell culture.