Abstract:Yunnan Longling Dendrobium devonianum Paxt.were used as the raw material，and Dendrobium devonianum Paxt.polysaccharide（DDP）were extracted using microwave-assisted immersion and selenized with sodium selenite using glacial acetic acid as the catalyst to form Se-DDP.Selenium content was determined using inductively coupled atomic emission spectroscopy，and Se-DDP was characterized using Fourier-transform infrared spectroscopy.The reaction conditions for selenium were optimized using single factor experiment and orthogonal experiment with selenium content on the refractive index.The scavenging ability of Se-DDP towards 1，1-diphenyl-2-picrylhydrazyl（DPPH），OH，and O2-free radical was determined.The optimal preparation process conditions for Se-DDP，i.e.，DDP：sodium selenite of 1∶2.0（g/g），90 ℃ reaction temperature，DDP∶ice acetic acid of 1∶4.0（g/mL），48-h reaction time，provided Se-DDP with a selenium content of 12.37 mg/g.Antioxidant experiments revealed that Se-DDP cleared DPPH，OH，and O2-free radical capacities better than DDP，when concentrations exceeded 4 mg/mL.When the concentration was 8 mg/mL，the Se-DDP antioxidant capacity was comparable to ascorbic acid（VC）.