Oxidative stress is closely related to the occurrence and development of ischaemic stroke. Natural plant polysaccharides have potential value in inhibiting oxidative stress and preventing ischaemic stroke. Here, a novel neutral polysaccharide named LICP009-3F-1a with a Mw of 10,780 Da was separated and purified from Lycium barbarum L. fruits. Linkage and NMR data revealed that LICP009-3F-1a has the following backbone: →4)-β-D-Glcp-(1→6)-β-D-Galp-(1→, with a branched chain of β-D-Galp-(1→3)-β-D-Galp-(1→, α-L-Araf-(1→ and →6)-α-D-Glcp-(1→ connected to the main chain through O-3 of →3,6)-β-D-Galp-(1→. X-ray and SEM analyses showed that LICP009-3F-1a has a semicrystalline structure with a laminar morphology. Thermal property analysis showed that LICP009-3F-1a is thermally stable. In vivo experiments suggested that LICP009-3F-1a could inhibit hypoxia-induced oxidative stress damage by eliminating ROS, reversing and restoring the activities of the antioxidant enzymes SOD, CAT, and GPx, and reducing the expression levels of the HIF-1α and VEGF genes. Blocking the apoptosis genes Bax and Caspase 3 and upregulating the expression of the antiapoptotic gene Bcl-2 protected PC12 cells from hypoxia-induced apoptosis. These results suggest that LICP009-3F-1a may have multiple potential uses in the treatment of IS.