Defatted rice bran was used as medium materials. By comparing the effects of microbial species， fermentation time， fermentation temperature and inoculation amount on the content of free phenolics in rice bran， the solid state fermentation conditions of rice bran were optimized. The contents of free and bound phenolics and flavonoids in rice bran before and after fermentation were determined， as well as the compositions and contents of individual phenolics and their antioxidant activity were also analyzed. Result: The Rhizopus oryzae strain had the strongest fermentation ability of increasing the content of free phenolics to a maximum of 612.29 mg GAE/100 g dw in rice bran. The optimum solid state fermentation conditions of rice bran with Rhizopus oryzae were as follows: the fermentation time was 5 days， the fermentation temperature was 30 ℃， and the inoculation amount was 1%. Under this condition， the contents of free phenolics and flavonoids in fermented rice bran were 162.2% and 58.4% higher than those in unfermented rice bran， respectively， but there was no significant difference in the contents of bound phenolics and flavonoids in rice bran before and after fermentation. Compared with the unfermented rice bran， the contents of free and bound phenolics changed significantly； Among them， the content of gallic acid had the most increased by 2.44 times and 8.11 times， respectively； The ABTS， FRAP， and ORAC antioxidant capacities of free phenolic in rice bran were significantly increased by 100.7%， 71.3%， and 67.0%， respectively. Conclusion: Solid-state fermentation of rice bran with Rhizopus oryzae could significantly improve the release of bound phenolic， increase the content of total phenolics， and enhance the total antioxidant activity.