Effects of the increase of the selenium-modified rate on the structural characteristics and antioxidant abilities of the selenized polysaccharides (Se-PS) were seldom reported. In this work, LBP1-1 purified from Lycium barbarum polysaccharides (LBP) was selenized by the subcritical water (SW) versus the traditional hot water (HW) method to obtain Se-modified SW-SeLBP1-1 and HW-SeLBP1-1, respectively. The results revealed that SW-SeLBP1-1 contained 17.49 ± 0.35 mg Se/g, significantly higher than 5.68 ± 0.05 mg/g of HW-Se-LBP1-1 and the reported before. The selenization time was reduced from 7 h to 20 min. Se modifications were mainly achieved by Se substitutions of hydrogen atoms in hydroxyl groups of LBP1-1. Xylose and galactose in LBP1-1 could be easily and regularly modified by Se, the Se modifications of the other monosaccharides showed significant different between the two methods. The generated C-O-Se groups could readily make SW-SeLBP1-1 formed a more orderly network structure than that of HW-SeLBP1-1 when Se-modified rate increased 11.81 %, resulting in its antioxidant activities increasing over 17.3 % in vitro.