Abstract: Objective To study the effects of diallyl sulfide(DAS) on apoptosis in cells and reactive oxygen species (ROS) generation induced by microcystin-LR(MCLR).Methods Human hepatoma cell line HT17 were treated with solvent alone or 1μmol/L MCLR in the presence or absence of DAS(0.02-2 mmol/L) for 4 hr or 24 hr.Then the cell viability was measured by methyl thiazolyl tetrazolium(MTT) assay,and the generation of ROS was determined by fluorescent probe 2-6-(4'-hydroxy) phenoxy-3H-xanthen-3-on-9-yl benzoic acid.Results The cell viabilities in 0.2 and 2 mmol/L DAS intervention group were 80.91±5.25% and 90.13±4.47%,significantly higher than that of MCLR-treated group (69.50±3.03%,P< 0.05).The percentages of apoptosis in 0.2 and 2 mmol/L DAS intervention group were 10.87±0.52% and 8.52±0.55%,significantly lower than that of MCLR-treated group (13.29±1.16%,P< 0.05).The levels of ROS in 0.2 and 2 mmol/L DAS intervention group decreased significantly (P< 0.05).Conclusion The results suggest that DAS inhibits both ROS generation and cell apoptosis induced by MCLR in HT17 cells.