Abstract: This study aimed to investigate the effects of chitosan-thymol composite solution on the quality and microbial communities of largemouth bass under storage at 4 ℃ and 10 ℃. Using the dorsal muscle of the bass as the experimental material, a 0.5% (m/v) chitosan solution (CH), a 0.1% (m/v) thymol solution (TH), and a composite solution of the two (CT) were prepared, with ultrapure water as the control (CK). Indicators such as total volatile basic nitrogen (TVB-N), total plate count (TVC), pH, biogenic amines, nucleotides, electronic nose analysis, sensory evaluation, and GC-MS volatile component analysis were measured during storage at 4 ℃ and 10 ℃, and bacterial community diversity was analyzed combined with 16S rRNA gene sequencing. TVB-N and TVC results showed that compared to CK, the CT group extended the shelf life by at least 9 days and 3 days at 4 ℃ and 10 ℃ respectively. The CT group significantly inhibited the formation of biogenic amines such as putrescine (Put), cadaverine (Cad), and histamine (His) as well as hypoxanthine (Hx), exhibited minimal pH fluctuation, reduced the formation of volatile compounds, delayed the accumulation of spoilage-related substances such as hexanal, nonanal, and 1-octen-3-ol, and promoted the retention of flavor compounds such as 2-methyl-3-pentanone and methyl butyrate. In sensory evaluation, the CT group showed better odor, color, and overall acceptability. Bacterial community analysis indicated that the dominant phyla were Firmicutes, Actinobacteria, and Proteobacteria. The CT group inhibited spoilage bacteria such as Acinetobacter and Pseudomonas, reducing microbial diversity. Genera such as Macrococcus and Acinetobacter were positively correlated with TVC, TVB-N, and spoilage indicators such as methyl butyrate. Therefore, this study demonstrates that the chitosan-thymol composite solution (CT) can effectively inhibit the growth of spoilage bacteria and extend the shelf life of largemouth bass.