Abstract: The purpose of this study was to explore the fermentation state and bacterial community structure of fermented grains during the stacking fermentation of Maotai-flavor Baijiu. The ''FD technology'' was applied to the stacking fermentation in second round of fermented grains production, and the changes of physicochemical factors and bacterial community in fermented grains during stacking fermentation were studied. Results showed that, compared with stacking fermentation of traditional fermented grains, the acidity of fermented grains of ''FD technology'' decreased by 1.72 mmol/10 g and the moisture content was kept to ±0.8%. The ''FD technology'' could effectively promote starch transformation (increased by 0.76%), and the reducing sugar content was increased by 0.46%. The Shannon, Sobs and Ace index of bacterial community in fermented grains increased significantly (P<0.05). On the level of microbial genus classification, the richness and diversity of microorganisms from fermented grains of ''FD technology'' significantly increased, which was conducive to the growth of aerobic bacteria such as Bacillus, and high-temperature resistant bacteria such as Thermoactinomyces. In conclusion, the ''FD technology'' could improve the uneven stations in the stacking fermentation of fermented grains, and the bacterial richness and diversity of fermented grains significantly increased, which was conducive to the growth of dominant aerobic and high-temperature resistant bacterial communities.