bjective:This study aimed to explore the composition, antioxidant activity and stability of purple potato polysaccharides and improve the efficiency of separation purification.Methods:The free radical scavenging capacity, antioxidant capacity and chemical stability of the crude polysaccharides from purple sweet potato were compared and analyzed by fractional alcohol precipitation.Results:The contents of polysaccharide, protein, sulfate group and uronic acid in the three fractions were in the order of PPSP-80% ＞ PPSP-60% ＞ PPSP-40%. Among them, PPSP-80% fraction had the strongest scavenging ability on DPPH, ABTS and superoxide anion free radicals, while PPSP-60% fraction had the strongest scavenging ability on hydroxyl free radicals. Whereas, PPSP-40% fraction had the worst scavenging ability on free radicals. The order of antioxidant effect on rapeseed oil was PPSP-80%＞PPSP-60%＞PPSP-40%, and PPSP-40% fraction had the worst stability, PPSP-60% had the best stability under extreme alkaline conditions, and PPSP-80% had the best stability at 121 ℃.Conclusion:Fractional alcohol precipitation has certain separation effect on purple sweet potato crude polysaccharides, and different alcohol precipitation components have obvious differences in antioxidant effect and stability. Therefore, the high concentration alcohol precipitated component had better antioxidant effect and stability.