Abstract: Objective To investigate the effects and mechanism of B-carotene on the injury of alveolar macrophage exposed to Ni₂O₃.Methods The alveolar macrophage was cultured in vitro with exposure to Ni₂O₃ and the detection of malondialdehyde and activity of antioxidant enzyme in alveolar macrophage were carried out.Results The results of adding different dose of β-carotene(25,50,100μmol/L)could increase the activity of superoxide dismutase in alveolar macrophage with an dose-dependent manner.Vitamin E could inhibit the production of malondialdehyde apparently.Both of the β-carotene 50μmol/L group and 100μmol/L group had dramatic inhibitory effect.Conclusion Ni₂O₃ could induce over-oxidation of cytoplasm β-carotene could inhibit the cytotoxity of Ni₂O₃,which probably due to its antioxidant property.