The polysaccharides of the asparagus old stalks was seperated by ethanol precipitation and ultrafiltration. The molecular weigh distribution and antioxidative capacity of the extracts of the alcohol precipitation(C-1), ultrafiltration retention(C-2), and ultrafiltration penetrates (C-3) were further evaluated. The polysaccharides yields of the C-1, C-2, and C-3 were 1.53, 1.21, and 0.71%, respectively. The weigh average molecular weight of C-1, C-2, and C-3 were 163900, 135880, and 61063 Da, respectively. C-2 showed the strongest antioxidant capacity in all extracts by the scavenging effect on DPPH, superoxide and hydroxyl radicals. Therefore, the ultrafiltration was an alternative to separate the polysaccharides from the asparagus old stalks and kept their antioxidatant capacity.