Monitoring the changes of bacterial communities during ensiling enables to understand and manipulate the fermentative process. In this context, it was explored the succession of bacterial populations and evaluated the impacts caused by microbial inoculants on bacterial community of rehydrated corn and sorghum grain silages by 16S rRNA Illumina MiSeq sequencing. A 2 × 3 × 6 factorial scheme was used, with 2 grains (corn -CG and sorghum-SG), 6 fermentation periods (0, 3, 7, 21, 90 and 360 d) and 3 inoculants: CTRL: non-inoculated; Inoc1: Lactobacillus plantarum and Propionibacterium acidipropionici (Lalsil Milho, Lallemand Animal Nutrition) and Inoc2: Lactobacillus buchneri (Lalsil AS, Lallemand Animal Nutrition), with 3 replicates in a completely randomized design. Grains were rehydrated with water to moisture content at 30%, inoculated and packed into plastic film bags (25.4 cm × 35.56 cm). The predominance (>80%) of Proteobacteria was observed in both grains at the beginning of the fermentation (d 0) except in CG-CTRL and CG-Inoc1 silages, which had 51% of Proteobacteria and 61% of Actinobacteria, respectively. In all CG silages Firmicutes philum predominated (>84%) from 3 to 90 d after fermentation. As early as 3 d of fermentation, it was observed 85% of Firmicutes in SG-Inoc1, which unlike CG silages, the predominance of this phylum was extended up to 360 d. The Bacilli and Gammaproteobacteria classes were the main representatives of the Firmicute and Proteobacteria phyla, respectively. In CS-CTRL the fermentation from the 3rd day was predominantly by Weissella spp. with gradual replacement by the Lactobacillus genus. Bacteria present in Inoc1 induced the predominance (>80%) of Lactobacillus from 3 to 90 d of fermentation. The SG samples had lower initial diversity which was a reflection of the predominance (51–80%) of the Pantoea genus, mainly in SS-Inoc1 silages (80%). Species of Lactobacillus and Weissella are the main genera involved in the fermentation of rehydrated silages of corn and sorghum grains. The inoculant containing L. plantarum and P. acidipropionici resulted in a sharply growth of Lactobacillus and greater stability of the bacterial community during long period of storage in both grain silages. Supported by CNPq, CAPES, and INCT-CA