Abstract: Bacterial community structure and succession in traditional fermented Sichuan chili sauce during natural fermentation were analyzed by high-throughput sequencing technology. The results showed that there were mainly Firmicutes,Proteobacteria and Bacteroidetes at bacterial phylum level in naturally fermented chili sauce. Firmicutes gradually increased with the progress of fermentation,and the relative abundance reached 28.56% on the 15th day of fermentation,which led it became to the highest phylum. On the genus level,there were mainly Lactobacillus spp.,Pediococcus spp.,Weissella spp. and Staphyloccoccus spp.. Lactobacillus spp. was the main dominant genus of the chili sauce. The abundance level of Lactobacillus was low during 0~25 d,and the relative abundance reached 68.24% at the 30th day of fermentation. Moreover,pathogenic bacteria such as Enterobacter spp. were detected,indicating that the microbial health and food safety issues existed during the natural fermentation of chili sauce.