The antioxidative activity of Astragalus Polysaccharides in different concentration in and out of SH-SY5Y cells was studied, and the antioxidative and free radical scavenging ability of Astragalus polysaccharides was evaluated. DPPH method was used to detect the antioxidant effect in vitro. It was found that with the increasing concentration of Astragalus polysaccharides, the scavenging rate of free radicals also increased. DCF method was used to study the scavenging effect of Astragalus Polysaccharides on intracellular ROS free radicals and the protective effect on cell viability. The results showed that the scavenging effect was consistent with the results of extracellular activity, and the protective effect of 75 mg / mL for 3 h on cell oxidative damage and cell death caused by H2O2 was the best. The results showed that Astragalus Polysaccharide had a good ability of scavenging free radicals.