[Objective] This study aimed to elucidate the bacterial community succession and its underlying relevance to the environmental factors in fermented grains of Luzhou-flavor baijiu. [Methods] The 16S rRNA gene amplicon sequencing analysis was applied to reveal the succession of bacterial community in the fermented grains, and Mantel test was used to correlate bacterial community succession with environmental factors. [Results] A total of 397 bacterial genera were identified in fermented grains, including Lactobacillus, Bacillus, Weissella, Dysgonomonas, Comamonas and Ruminococcaceae (relative abundance>1.0%). Fermentation process was divided into three stages:stage I (0-5 d), stage Ⅱ (6-17 d) and stage Ⅲ (18-40 d) according to clustering analysis, and the bacterial community structure was significantly different among these three stages. Metastats analysis demonstrated that the relative abundance of Lactobacillus and unclassified Lactobacillales in stage Ⅱ was significantly higher than that in stage I (P<0.05), whereas the situation of unclassified Bacillaceae, Staphylococcus, Bacillus, unclassified Enterobacteriaceae, Lactococcus, Pseudomonas, Thermoactinomyces, Leuconostoc and Staphylococcus quite the reverse (P<0.05). Compared with stage Ⅱ, the relative abundance of Lactobacillus increased in stage Ⅲ (P<0.05), conversely, downregulation dominated Comamonas, Acetobacter, unclassified Bacilli, Clostridium, Bacillus, Ruminococcus, unclassified Porphyromonadaceae and unclassified Streptophyta (P<0.05). Results of Mantel test indicated that the bacterial community succession in the stage I was correlated with the dynamics of temperature, moisture, and alcohol concentration (P<0.05), whereas no significant correlation was observed between environmental factors and bacterial community succession in the stage Ⅱ and Ⅲ (P>0.05). [Conclusion] Our work demonstrated the dramatically divergent bacterial community structure in the fermented grains of Luzhou-flavor baijiu from different brewing stages. Temperature, moisture and alcohol concentration significantly correlated with the bacterial community succession in early stage of fermentation (0-5 d).