Abstract: To investigate the effects of chitosan coatings with high (300 kDa), medium (150 kDa), and low (20 kDa) molecular weights on the quality of refrigerated turbot fillets, the changes in microbial count, total volatile basic nitrogen (TVB-N), pH, K value, thiobarbituric acid (TBA), biogenic amines, texture, color difference, fatty acid composition, and sensory characteristics of the samples were analyzed during storage at 4 ℃. The results showed that, compared with the control group without chitosan treatment, the chitosan coatings significantly reduced the total number of colonies in the samples (P<0.05). Meanwhile, it significantly inhibited the growth of Pseudomonas, hydrogen sulfide-producing bacteria, and Enterobacteriaceae (P<0.05). Moreover, the inhibitory effects varied among the chitosan-coated samples. Specifically, the total number of colonies and hydrogen sulfide-producing bacteria quantity of the low molecular weight chitosan-coated samples were the lowest. The lowest TVB-N and TBA values after refrigeration were observed in the low molecular weight chitosan-coated fillets, with reductions of 48.04% and 32.91% compared to the control group, respectively. In addition, the low molecular weight chitosan coating effectively maintained the texture, color difference, and sensory quality of the fillets. The K values of the chitosan-coated groups on the 15th day was significantly lower than that of the control group (P<0.05), while there was no significant difference among the chitosan-coated samples (P>0.05). The content of unsaturated fatty acids in the chitosan-coated samples was higher than that in the control group at the end of storage, and the low molecular weight chitosan-coated samples showed the highest relative abundance of n-3 polyunsaturated fatty acids. Pearson correlation analysis and Mantel test further confirmed that the low molecular weight chitosan coating (1%) could maintain the stability of unsaturated fatty acids during refrigeration at 4 ℃ for 15 days. In conclusion, chitosan coatings with different molecular weights, especially the low molecular weight chitosan coating, can effectively prevent the deterioration of fillets caused by microbial growth and lipid oxidation.