This study innovatively explores flax polysaccharides as sustainable sand-fixing agents, addressing the long-standing challenge of degumming-wastewater pollution. By utilizing polysaccharide-rich components in the wastewater to bind sand particles, the research systematically investigates the formation mechanisms, structural properties, and water retention capabilities of sand crusts. Key findings reveal that high-molecular-weight polysaccharides (M-w > 10(5)) are essential for crust formation, while low RG-I (<2.0 g/L) and protein (<1.7 g/L) concentrations negatively impact fixation efficiency. Under optimized conditions (4.8 g/L polysaccharides, 2.2 g/L lignin, 1.4 g/L protein, 1.5 g/L RG-I), an ideal sand crust with a hardness of 1.4 kg/cm(2) and a thickness of 25.3 mm can be fabricated. In water-deficient environments, the seed germination rate of the polysaccharide crust reaches 54 %, which is considerably higher than the 42 % of the PVA crust and 36 % of the lignin crust. This can be ascribed to the outstanding water-retaining property of the polysaccharide materials. Overall, flax degumming wastewater emerges as an exceptional and underexplored resource for the production of eco-friendly sand-fixing agents, presenting great potential for sustainable desertification control and ecological restoration in arid regions.