For further utilization of mussel resources and innovate mussel food types， mussel bean paste products were developed with mussel， soybean and rice as raw materials， Aspergillus oryzae koji making and mixed fermentation， and its volatile flavor substances and in vitro antioxidant activity were evaluated. Through single factor experiment， the optimal fermentation conditions of mussel bean paste were determined: salt addition 14%， Koji and mussel mass ratio 1 ∶ 1， fermentation temperature 40 ℃， fermentation time 24 d. Under these conditions， the sensory score of mussel bean paste was the highest 92 points， and the content of amino acid nitrogen was 0.84 g/100 g. Compared with the non fermented samples， the mussel bean paste fermented by Aspergillus oryzae had more volatile compounds， and the relative contents of aldehydes， esters and other characteristic flavor substances increased by 11% and 19.4%， respectively. FRAP ability and hydroxyl radical scavenging ability of the mussel bean paste were significantly enhanced. The preparation of mussel bean paste by Aspergillus oryzae fermentation provides a new way to enrich the variety of mussel products.