To investigate whether microcystin-LR (MC-LR) at doses which were not cytotoxic can induce DNA damage and compare its effect on HL-7702 and KB cell lines.Cytotoxin and DNA damage were detected by MTT and comet assay, respectively.As doses ranged from 10 to 100 micro/L, MC-LR showed no significant impact on viability of these two cell lines. However, DNA damage induced by MC-LR occurred at the dose of 30 microg/L in HL-7702 cell and significantly increased with dose. MC-LR did not induce DNA damage in KB cell.MC-LR has potential genotoxicity, DNA damage induced by MC-LR is more significant in hepatocyte with bile acid transportation system than other cell lines.