The invention provides mytilus edulis polysaccharide extracted from mytilus sp., an industrial extraction method of the mytilus edulis polysaccharide, and an application of the mytilus edulis polysaccharide in preparation of antilipemic and antiatherosclerotic drugs and health food. The mytilus edulis polysaccharide takes (1-4)-alpha-D-Glc as main chains, contains (1-2)-alpha-D-Glc branches, and has a configuration of alpha-pyranoid glucan; every 12 glucose main chains averagely contain one (1-2) glucose branch; and the relative molecular weight is 800-8000KDa. The mytilus edulis polysaccharide is extracted from boiled and dried mytilus sp. by coarse extraction, enzymolysis, purification, drying and the like, and is mild in extraction condition and high in purity. The mytilus edulis polysaccharide can significantly reduce triglyceride, total cholesterol and low-density lipoprotein cholesterol, has an effect of reducing lipid, and is widely applied to preparation of drugs for treating or preventing hyperlipoidemia and atherosclerosis and preparation of antilipemic health products or special medical formula food.