AIM: To observe the physicohemical properties and antioxidant activities of polysaccharides isolated from Inonotus obliquus by physical modified, and furthermore, to evaluate the modified methods used in processing Inonotus obliquus polysaccharide (IOPS).METHOOD: At present polysaccharides from Inonotus obliquus were modified by acid, alkali hydrolysis, thermal and ultrasonic treatment.The physicochemical and antioxidant properties of IOPS and its resulted products were comparatively investigated by chemical methods, gas chromatography, size exclusion chromatography, scanning electron micrograph and circular dichroism spectra, and ferric reducing power assay and lipid peroxidation inhibition assay, respectively.RESULTS: Results showed that physicochemical and antioxidant properties of IOPS differed each other after the physical modification of acid, alkali hydrolysis, thermal and ultrasonic treatment.Thermal treated polysaccharide (Th-IOPS) and ultrasonic treated polysaccharide (Ul-IOPS) resulted in lower molecular weight distribution, lower intrinsic viscosity, a hyperbranched conformation, higher antioxidant abilities on ferric-reducing power and lipid peroxidation inhibition activity compared with the native polysaccharide IOPS.CONCLUSION: Th-IOPS and Ul-IOPS might be explored as a novel potential antioxidant for human consumption.