Objective：This study aims to investigate the effect and mechanism of fucoidan inhibiting inflammatory bowel disease（IBD）. Methods：Mice were randomly divided into experimental group and control group（n=5，each group）. The experimental group was intragastrically with fucoidan，meanwhile，the control group was given drinking water. Two weeks later，both groups drank dextran sulfate sodium salt（DSS） to make mouse model of IBD. Body weight，spleen weight，colon length and weight of mouse were measured. Pathological changes of colon tissue was observed by HE staining，stool property was observed and scored，and mRNAs of inflammatory factors，chemokines and tight junction proteins were detected by real-time fluorescence quantitative PCR. Results：Intestinal inflammation related indexes were better in experimental group treated with fucoidan than in the control group，and the degree of inflammation was reduced. Conclusion：Fucoidan can prevent and inhibit the occurrence of IBD. This study will provide a new method and evidence for the prevention and treatment of IBD.