Cancer is the most common disease worldwide, with death often occurring as a result of metastasis. Thus, interfering with metastasis has been regarded as a promising strategy to improve the current cancer treatments. However, exploration and development of novel anti-metastatic agents remains a major challenge. Recent evidence indicated that a polysaccharide isolated from Taxus yunnanensis suppressed tumor cells proliferation. With the objective of seeking bioactive extracts, we had previously isolated, purified and characterized a complex, water-soluble polysaccharides, PSY-1, from the leaves of Taxus chinensis var. mairei, and identified its anti-neoplastic effects. In this study, we focused on the effects of PSY-1 on cancer metastasis and its mechanism(s). The results illustrated that PSY-1 effectively suppressed the migration and invasion ability of the melanoma cancer cell line B16-F10, caused down-regulation of MMP-2 and MMP-9, and that the NF-kappaB pathway was involved in the anti-metastatic effects imposed by PSY-1.