Tartary buckwheat (Fagopyrum tataricum) has been consumed in China as health food and medicine. In this study, the ethanol extract (EE) of tartary buckwheat was prepared. The major flavonoid in EE was identified as rutin by HPLC-PDA-ESI/MS and the content of rutin in EE was determined as 27.4 % by HPLC. In the anticancer assay, it was found EE could inhibit the proliferation of the human hepatocellular liver carcinoma Hep G2 cell line in a dose-dependent manner. The increase of an early apoptotic population was observed by both annexin-FITC and PI staining, which suggested that EE could induce Hep G2 cells to enter into apoptosis.