This study aimed to develop an efficient method for the extraction of Ulva polysaccharides, which have shown promising biological activities such as antiviral, antitumor, and anti-plasmodial effects. The researchers used ultrasound-assisted enzymatic extraction (UAE) to improve the extraction yield and biological activity of Ulva polysaccharides. They screened cell wall-degrading enzymes, including cellulase, hemicellulase, pectinase, and protease, and found that a mixture of these enzymes significantly increased the polysaccharide yield from 6.43% to 26.68%. Further optimization using response surface methodology (RSM) identified the optimal extraction conditions: enzyme concentration of 1.5%, enzymatic time of 1.1 hours, ultrasonic time of 90 minutes, and enzymatic temperature of 60°C, resulting in a polysaccharide yield of 30.14%. The extracted polysaccharides exhibited strong antioxidant properties, effectively scavenging DPPH, hydroxyl, ABTS, and superoxide radicals. Additionally, the polysaccharides protected SH-SY5Y cells from H₂O₂-induced oxidative damage, increasing cell viability. This study provides a solid foundation for the commercialization and further development of Ulva polysaccharides.This study aimed to develop an efficient method for the extraction of Ulva polysaccharides, which have shown promising biological activities such as antiviral, antitumor, and anti-plasmodial effects. The researchers used ultrasound-assisted enzymatic extraction (UAE) to improve the extraction yield and biological activity of Ulva polysaccharides. They screened cell wall-degrading enzymes, including cellulase, hemicellulase, pectinase, and protease, and found that a mixture of these enzymes significantly increased the polysaccharide yield from 6.43% to 26.68%. Further optimization using response surface methodology (RSM) identified the optimal extraction conditions: enzyme concentration of 1.5%, enzymatic time of 1.1 hours, ultrasonic time of 90 minutes, and enzymatic temperature of 60°C, resulting in a polysaccharide yield of 30.14%. The extracted polysaccharides exhibited strong antioxidant properties, effectively scavenging DPPH, hydroxyl, ABTS, and superoxide radicals. Additionally, the polysaccharides protected SH-SY5Y cells from H₂O₂-induced oxidative damage, increasing cell viability. This study provides a solid foundation for the commercialization and further development of Ulva polysaccharides.