Carboxymethyl pachymaran （CMP） is a carboxymethylated modification product of the water-insoluble polysaccharides from Poria cocos. It has many biological activities such as immune regulation, antibacterial, anti-inflammatory, anti-tumor, anti-oxidation, liver damage protection and intestinal flora regulation. It has a wide application prospect in functional food, active molecular carrier, medicine and other fields. In this paper, the research of CMP at home and abroad in recent years was focused, the biological activity, preparation, identification and application development of CMP were reviewed, and the future development direction of CMP was prospected.