The hot water and mathanol extracts of Artemisia argyi showed considerable cytotoxicities against H9(ATCC HTB 176) cancer cell with IC50 values of $48.6{;}mu extrm{g}/ml$ and $51.9{;}mu extrm{g}/ml$, respectively. These cytotoxicities were found to be dependent on the extract concentrations and culture days. CuZnSOD and MnSOD activities were significantly increased in the cytoplasm and mitochondria fractions of cancer cell, and media in the presence of Artemisia argyi. Such enhanced SOD activities were generally in the range of two to threefolds. In contrast to SOD, catalase and glutathione peroxidase activities were not detected at all. These results suggest that Artemisia argyi have generated $O_2^-$ in the mitochondria and cytoplasm of H9 cancer cell with concurrent induction of CuZnSOD and MnSOD in situ, which dismutate $O_2^-{}to{;}H_2O_2$. Without coordinated actions of catalase and/or glutathione peroxidase $H_2O_2$ is easily converted to very toxic OH and these reactive oxygen species together might have induced necrosis and/or apoptosis of H9 cell.