Morchella esculenta is a precious edible and medicinal fungus, rich in active substances such as polyphenols, polypeptides and polysaccharides. M. esculenta polysaccharides (MEP) are a class of carbohydrates formed by the polymerization of aldose or ketose through glycosidic bonds, exhibiting a variety of biological activities including immune regulation, hypolipidemic effects, and anti-fatigue properties. With the deepening of research, the market demand for MEP is constantly increasing, making it particularly important to optimize its extraction and purification processes. Immune regulation is a key process in living organisms, and as the main active ingredient, MEP has attracted significant attention for its immunoregulatory function. However, its specific mechanism of action and structure-activity relationships remain unclear. This study reviews different extraction and purification methods of MEP, as well as the structural differences and immunoregulatory activity mechanisms of polysaccharides, and analyzes the structure-activity relationships.