As of 2023, the National Health Commission has announced 102 MEHs varieties, with 94 being plant-erived. Their development and application show great potential. The plant polysaccharides (MEHPPs) are one category of the main and representative pharmacologically active macromolecules in MEH that have many biological activities both in vitro and in vivo, such as immune regulation, antioxidant, hypoglycemic, lipid-lowering, antitumor, anti-inflammatory, etc. In addition, the quality of MEHPPs obtained from different raw materials via sundry extraction and purification methods is different. At the same time, the structural analysis of MEHPPs is the focus of studying the molecular weight determination, monosaccharide composition, glucoside linkage mode, and partial conformation. Based on the literature search, this article reviews the preparation methods, structural characterization, biological activities, and potential mechanisms of MEHPPs. It provides a basis for the development of safe and effective health care products and new drugs for the prevention and treatment of many chronic diseases.