In order to explore whether co-fermentation of garlic and ginseng could affect the microbial diversity, chemical composition and physiological function of black ginseng, fresh garlic and ginseng were used as raw materials to make black garlic, black ginseng and ginseng garlic by liquid-state fermentation. During the fermentation process, their microbial diversity, major components and antioxidant properties were analyzed. The results showed that the dominant bacterial phylum in ginseng garlic was Firmicutes, and the dominant bacterial genera included uncultured_bacterium_f_Muribaculaceae and Lactobacillus. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that there were no obvious differences between the metabolic pathways of ginseng garlic, black garlic and black ginseng, mainly including Global and overview maps, carbohydrate metabolism and amino acid metabolism. The contents of reducing sugars and total phenols in ginseng garlic were significantly increased, the total acid content was decreased, the conversion rate of rare ginsenosides was significantly increased, and the content of the potential harmful substance 5-hydroxymethylfurfural(5-HMF) was significantly reduced. Moreover, ginseng garlic had good free radical scavenging capacity. The above findings provide a theoretical basis for the development of ginseng garlic products and for promoting the development of the black ginseng industry. © 2022, China Food Publishing Company. All right reserved.