Fucoidan is a uniquely-structured sulfated polysaccharide found in the cell walls of several types of brown Seaweed that has recently, especially as Enzyme-digested Fucoidan extract, attracted a lot attention due to its anti-Tumor potential. In this study, we evaluated the effects of Enzyme-digested Fucoidan Extracts prepared from Seaweed Mozuku of Cladosiphon novae-caledoniae kylin on in vitro Invasion and Angiogenesis abilities of human Tumor Cells. First, we evaluated the effect of the Fucoidan Extracts on oxidative stress of Tumor Cells, and demonstrated that intracellular H(2)O(2) level and released H(2)O(2) from Tumor Cells were both greatly repressed upon the treatment with the Fucoidan Extracts, suggesting that Fucoidan Extracts ameliorate oxidative stress of Tumor Cells. Next, we tested for the effects of Fucoidan Extracts on Invasion ability of human fibrosarcoma HT1080 Cells, showing that Fucoidan Extracts significantly Inhibit their Invasion, possibly via suppressing matrix metalloproteinases (MMPs) MMP-2/9 activities. Further, we investigated the effects of the Fucoidan Extracts on Angiogenesis of human uterine carcinoma HeLa Cells, and found that Fucoidan Extracts suppressed expression and secretion of an Angiogenesis factor vascular endothelial growth factor (VEGF), resulting in suppressed vascular tubules formation of Tumor Cells. The results taken together clarified that Enzyme-digested Fucoidan Extracts from Cladosiphon novae-caledoniae kylin possess Inhibitory effects on Invasion and Angiogenesis of Tumor Cells. These effects might, at least partially, be elicited by the antioxidative potential of Enzyme digested Fucoidan Extracts.