The polysaccharide was extracted by the ultrasonic-assisted aqueous two-phase technology from germinated brown rice. The phase separation ability of different in PEG/(NH₄)₂SO₄ system was studied according to the polysaccharide yield. The yield of polysaccharide substance of germinated brown rice was determined by orthogonal experiment. The optimum process conditions were determined. Results were showed as follows: the mass fraction of PEG6000 was 15.7%, the mass fraction of ammonium sulfate was 14.8% and extraction time was 40 min. The yield of polysaccharide substance from germinated brown rice was 81.07% in the optimum conditions. Morever, the anti-oxidation of polysaccharide substance from germinated brown rice were studied by methods of DPPH, pyrogallol autoxidation and phenanthroline. The results showed that the polysaccharide of brown rice had stronger antioxidant effect to DPPH, ultra oxygen anion and hydroxyl radicals.