Abstract: In order to investigate the effects of chili peppers on volatile compounds and bacterial community composition in shrimp paste, this study applied chili peppers to the fermentation of shrimp paste and compared it with the fermented shrimp paste without chili peppers, determined volatile compounds by gas chromatography-ion mobility spectrometry (GC-IMS), and analyzed the phylum- and genus-level compositions of the bacterial community and the changes in diversity by high-throughput sequencing (HTS), and established the correlation between dominant genera and key volatile flavor compounds by Spearson correlation analysis (SCA) The results showed that the addition of chili peppers increased the MDA content of shrimp paste during the fermentation process, and the flavor differences between the two groups of shrimp paste at the end of fermentation were small and acceptable. The addition of chili peppers introduced volatile flavor compounds such as 2-ethylfuran, β-pinene M, methyl tert-butyl ether D, 2,3-diethylpyrazine M, and propionaldehyde into the shrimp paste. As fermentation proceeded, flavor compounds such as 2,3-glutaraldehyde and 2-methylbutyraldehyde accumulated in the chili shrimp paste, and methyl tert-butyl ether, β-pinene, and other substances with some irritating odors decreased, resulting in a softer flavor. At the phylum level, the addition of chilli increased the relative abundance of Cyanobacteriota and Bacillota and decreased the relative abundance of Bacteroidota in shrimp paste. At the genus level, the addition of chilli introduced Oceanobacillus to the shrimp paste, increased the relative abundance of norank_o_Chloroplast, and decreased the relative abundance of Olleya and Flavobacterium. Candidatus_Bacilloplasma, unclassified_f_Paracoccaceae, as the core dominant genera shared by the two groups of shrimp paste, were significantly negatively correlated with the content of characteristic volatile compounds in chili peppers, such as 2-ethylfuran, and were also positively correlated with the major volatile flavor compounds generated in shrimp paste fermentation, such as butyl acrylate, which were a key microorganism driving the formation of flavor. The results of this study provide theoretical support for the development of novel flavor composite chili shrimp paste.