Polysaccharides are one of the four essential biomolecules for life and exhibit diverse biological activities and functional properties. The development and application of polysaccharides depend on the discovery of high-quality polysaccharides, the elucidation of their fine structures, and the advancement of their synthesis and preparation technologies. However, conventional extraction and research methods are plagued by high energy consumption, environmental pollution, and low efficiency. Polysaccharide green manufacturing technologies are designed to obtain, modify, and produce functional polysaccharides through environmentally friendly and sustainable approaches. Current research progress mainly involves three aspects: green extraction, green modification, and synthetic biology. Green extraction technologies achieve low energy consumption and high efficiency while maximally preserving the native structure of polysaccharides. On this basis, green modification technologies enable targeted structural modification, thereby improving the physicochemical properties and biological activities of polysaccharides. In addition, synthetic biology provides new strategies for the de novo design and controllable synthesis of polysaccharides with specific structures and functions. This review summarizes recent advances in the green extraction, green modification, and synthetic biology of polysaccharides, aiming to provide theoretical support and technical references for the sustainable development and high-value utilization of polysaccharide resources.