Abstract: The leaves and bagasse of sugarcane, an important food and economically significant crop, are recognized as two major residues. These materials are abundant in resources and rich in bioactive compounds, and their significant potential for the development of functional foods and health products is acknowledged. Polysaccharides are recognized as the main active components of sugarcane leaves and bagasse. Extraction is performed using traditional techniques with water and alkaline solutions as solvents, as well as auxiliary methods such as enzymatic, ultrasonic, microwave, and high-temperature-high-pressure extraction, which are based on the traditional techniques. Among these, the disruption of the lignin-carbohydrate complex (LCC) is recognized as key to improving polysaccharide extraction efficiency. Sugarcane leaves and bagasse are mainly composed of cellulose, hemicellulose, and water-soluble polysaccharides. Cellulose is mainly composed of β-glucans possessing a β-1,4-glucose main chain, and hemicellulose is generally composed of xylan with a β-1,4-xylopyranose main chain. The structures of water-soluble polysaccharides are considered more complex, being composed of various monosaccharides, such as mannose, glucose, galactose, and arabinose, along with various glycosidic linkages. Sugarcane leaves and bagasse polysaccharides are known to possess rich biological activities, including antioxidant, antibacterial, anti-tumor, diabetes-improving, anti-cardiovascular disease, immune-regulating and gastric-protective effects. They are considered to have great application potential in the fields of food, health products, and medicine. Although the physicochemical properties and activities of polysaccharides from sugarcane leaves and bagasse have been extensively studied, a need is recognized for better understanding of their precise structure, structure-activity relationship, and action mechanisms of various activities. Based on a comprehensive review of relevant literature, the extraction, isolation, purification, chemical structure, and biological activities of polysaccharides from sugarcane leaves and bagasse are systematically summarized in this paper. The current status of polysaccharide modification and application is also briefly analyzed, with the aim of providing a useful reference for further research and development of these polysaccharides.