Abstract: Objective To study the cyto to xicity induced by sodium arsenite(NaAsO₂),and co-treamtent of NaAsO₂ and buthion ine sulfox miine(BSO)on Chang liver cells.Methods Cultured Chang liver cells were exposed to NaAsO₂ a lone or co-exposed to NaAsO₂ and BSO for 24hr.Cellmorphology and viability were evaluated by inverted phase contrast micro scope and MTT a ssay.Results Cell morphology were changed and cell viability was decreased remarkably with dose-effect relationship under NaAsO₂(0-250Lmol/L)exposure(P<0.01).Cotreatment of NaAsO₂(5 and 20 Lmol/L)and BSO(1 mmol/L)significantly decreased the cell viability compared with the NaAsO₂ exposure groups(P<0.01).Conclusion NaAsO₂ shows obvious cytotoxicity,while co-treamtent of NaAsO₂ and BSO aggravates the cytotoxicity on Chang liver cells.