Purpose: This study was designed to investigate the anti-tumor metastasis by immunomodulating effects of extracts of Prunellae Spica. Methods: Antimetastatic experiment was conducted in vivo by using colon 26-M3.1 carcinoma. And we observed cytotoxicity of Prunellae Spica on colon 26-M3.1 carcinoma, L5178Y-R lymphoma cell, hela cell and macrophage. To observe the immnomodulating effects of Prunellae Spica, we estimated IL-6, IL-10, IL-12, TNF-${alpha}$ from peritoneal macrophages. And we evaluated the activation of NK cell by using anti-asialo-GM1 serum. Results: We found that the administration of Prunellae Spica extracts significantly inhibited tumor metastasis in vivo. In an in vitro cytotoxicity analysis, cell growth are closer to 100% in case of colon 26-M3.1 carcinoma, L5178Y-R lymphoma cell, hela cell at low concentration. In case of macrophage, cell proliferation is closer to 100% less than $62.5{mu}g/m{ell}$ of Prunellae Spica extracts. The level of cytokine such as IL-6, IL-10, IL-12 which stimulates Prunellae Spica extracts was increased in dose-dependent manner compared to the control group. TNF-${alpha}$ is hardly secreted less than $250{mu}g/m{ell}$ The depletion of NK cells by anti-asialo GM1 serum partly abolished the inhibitory effect of Prunellae Spica on tumor metastasis. Conclusion: Prunellae Spica appears to have considerable activity on the anti-metastasis by activation the immune system such as macrophage and NK cell.