Abstract: In this study, the model of mixed fermentation was constructed using the chicken and soybean, in order to explore its differences (on the content of protein, amino acid nitrogen, free amino acids, volatile flavor and on the activity of protease) from a single fermented soybean product. The results showed that fermentation induced a decline of the content of protein, but an increase in amino acid nitrogen, free amino acids and the activity of protease, respectively. The contents of fresh flavor amino acids and total free amino acids were significantly higher in the mixed chicken and soybean fermentation group than in the pure soybean fermentation at different fermentation periods (P<0.05), and the accumulation of volatile flavor substances was also higher than in the pure soybean fermentation. Compared with the soybean fermentation group, the mixed fermentation group had significantly higher concentrations of umami amino acids and total free amino acids, and richer volatile flavors during fermentation, in which 3-methylthiopropionaldehyde, benzaldehyde, phenylacetaldehyde, and 1-octen-3-ol were regarded as the key differential compounds by means of orthogonal partial least squares discriminant analysis (OPLS-DA) and odor activity value (OAV). The current study contributes to the development of new soybean-based condiment and provided a theoretical reference for quality control of soybean fermentation products.