Abstract: In this study,black highland barley was used as raw material to explore the dynamic changes of biochemical components during the fermentation of black highland barley with single and mixed strains of two lactic acid bacteria(R₁、R₅)and Rhizopus oryzae. Results showed that pH value of the black highland barley fermented by single R₅ decreased rapidly and reached the lowest level of 4.32±0.01,and the total acid content was significantly higher than other two strains,and finally reached 2.52%±0.12%. The reducing sugar content and alcohol content of black highland barley fermented with Rhizopus oryzae were significantly higher than that with R₁ and R₅,and the highest reached(6.94±0.22)and(9.19±0.49) mg/g,respectively. The ammonium nitrogen content of black highland barley with R₁ was closed to that with R₅. And the ammonium nitrogen content of the fermentation with R₁ and R₅ were higher than that with Rhizopus oryzae,and finally reached(0.10±0.01)and(0.11±0.01) mg/g,respectively. The results of mixed fermentation showed that the mixed fermentation could significantly improve the nutritional quality and improve the flavor of the sweet fermented black highland barley. Among them,the mixture of R₅ and Rhizopus oryzae fermented in the process of fermentation,the pH value decreased rapidly,which was decreased by(5.65±0.08)to(4.16±0.08),and the acid production was more,which was increased from 0.48%±0.03% to 7.16%±0.03%.During the fermentation,the final alcohol content was only(8.25±0.35) mg/g. The ammonium nitrogen content was finally reached(0.11±0.01) mg/g. At the same time,the sensory quality was better than other fermentations,the highest score at 48 h,reaching(86±0.89)points. It was suitable for fermentation to prepare the low-alcohol,high-nutrition of the sweet fermented black highland barley. However,the black highland barley fermented products with the mixture of R₁ and Rhizopus oryzae produced less acid,but the highest alcohol content eventually reached(9.80±0.60) mg/g. It was suitable to prepare the low-acid,high-alcohol of the fermented black highland barley product. Considering comprehensively,it was finally determined that the best time of the nutritional quality and sensory characteristic of the sweet fermented black highland barley by mixed solid-state fermentation was at 48 h. According to the quality and flavor requirements of the fermented black highland barley product,it could be selected a suitable mixed strains fermentation. This study could lay a foundation for the industrial production of the sweet fermented black highland barley.