Abstract: Objective To investigate the joint antagonism of manganese chloride and/or sodium selenite against DNA damage induced by silicon dioxide in lung cells of Chinese hamster. Methods Fibroblast cells were cultured with silica and manganese chloride(0.25,0.5 and 1.0 mg/L)and/or sodium selenite(0.5,1.0 and 2.0μmol/L).The damage was measured with comet assay. Results Manganese chloride and/or sodium selenite alone showed antagonism against DNA damage induced by silicon dioxide in lung cells of Chinses hamster.The most effective dosages were 1.0 mg/L of manganese chloride and 1.0 mg/L of sodium selenite for the combined antagonism of the two elements. Conclusion Manganese chloride and/or sodium selenite could reduce DNA damage induced by silicon dioxide in lung cells of Chinese hamster.