Abstract: In this paper, Cinnamomum cassia polysaccharide (CCP) was extracted and purified, and its physicochemical properties, antioxidant and hypoglycemic activities were investigated. The polysaccharide yield was optimized by the response surface test with three conditions: Temperature, time and liquid-solid ratio. Then the physicochemical properties of purified CCP were investigated by high performance liquid chromatography, thermogravimetric analysis and other methods, meanwhile, its antioxidant and hypoglycemic activities were tested in vitro. Results indicated that the optimum extraction conditions as follow: Extraction temperature 90 ℃, extraction time 2.5 h, liquid-solid ratio 20:1 (mL/g), extraction twice, under these conditions, the average yield was 3.22%. The relative molecular weight of CCP was 1.95×10⁶ Da, the total sugar content was 90.11%±1.24%, and it was stable within 230 ℃. Both Fourier-transform infrared and nuclear magnetic hydrogen spectra showed that CCP had α, β-glycosidic bonds and other structures, in addition, Congo red staining showed that it might not have triple helix structure. Activity assays showed that CCP had good scavenging effect on DPPH·, ABTS⁺∙, ·OH, with IC₅₀ values of 0.191, 2.835 and 3.221 mg/mL, respectively, and the total reducing power value of the polysaccharide at 6 mg/mL was 1.18. In addition, CCP also had inhibitory activity against α-amylase and α-glucosidase, with IC₅₀ values of 0.189 and 0.340 mg/mL. In this study, a high molecular weight Cinnamomum cassia polysaccharide was extracted and purified, which had good antioxidant and hypoglycemic activities, which may provide a basis for the functional development and utilization of Cinnamomum cassia.