To study the molecular mechanism of shikonin by activating reactive oxygen species ROS to induce apoptosis of colorectal cancer cellsMethods:The effect of shikonin on the viability of human colon cancer cell lines HCT116 and SW480 was detected by MTT assay，combined with Annexin V-FITC/PI apoptosis detection kit and flow cytometry to detect cell apoptosis; by Caspase 3/9 activity assay kit and caspase activity were was detectedROS detection kit was used to detect the effect of shikonin treatment on the ROS levels in HCT116 and SW480 cells，and the expression of Bcl-2 and Bcl-xL proteins was detected by Western BlottingResults:Cell viability test results showed that human normal colonic mucosal epithelial cell line NCM460 was not sensitive to shikonin intervention，while shikonin showed a significant inhibitory effect on human colon cancer cell lines HCT116 and SW480 cells(P<005)Western Blotting detected cyclin D and c-Myc，and Bcl-2 and Bcl-xL protein levels were significantly down-regulated after shikonin intervention(P<005)Meanwhile，shikonin increased the expression levels of Caspase3 and Caspase9 protein in a dose-dependent manner(P<005)Flow cytometry results showed that after treated with 10 μmol/L shikonin for 24 h，the apoptosis rate of HCT116 and SW480 cells increased to 592% and 656%，with almost no necrotic cells(Annexin V-，PI+); Mitochondrial membrane potentials to HCT116 and SW480 cells were depolarizedROS levels showed that shikonin up-regulated ROS levels in HCT116 and SW480 cells in a dose-dependent mannerConclusion:Shikonin induces apoptosis of colon cancer cells through mitochondria-mediated pathway，and Bcl-2 protein family and intracellular ROS levels play an important role in this process.