Abstract: This experiment aimed to investigate the bacterial composition of pre-fermented juice (PFJ) made from soybean, maize, okra, and pumpkin leaves and their effects on the fermentation quality of rice straw silage. This experiment included a control group and four kinds of PEJ treatment groups (a dose of 3%). The results showed that there were significant differences in the bacterial community structure among the 4 PFJ treated groups, but the dominant phyla were Firmicutes and Proteobacteria, and Lactococcus was the common dominant genus (relative abundances＞10.0%). Adding 4 kinds of PFJ significantly reduced the pH value, ammonia nitrogen, propionic acid, and butyric acid contents in rice straw silages, and significantly increased the lactic acid content. The relative abundances of Lactococcus, Enterococcus, and Latilactobacillus in the PFJ were significantly positively correlated with lactic acid and acetic acid contents, while the relative abundances of Pantoea and Enterobacter were significantly positively correlated with propionic acid, butyric acid and ammonia nitrogen contents. In summary, adding PFJ could effectively improve the fermentation quality of rice straw silage, and Lactococcus, Enterococcus and Latilactobacillus might be the key microorganisms.