Abstract: To investigate the effects of Bacillus subtilis on the hepatic lipid metabolism and antioxidant function, the grass carp were randomly divided into 4 groups: control group (Con), Aeromonas hydrophila group (Ah), Aeromonas hydrophila+Bacillus subtilis (Ah+Bs) group and Bacillus subtilis+Aeromonas hydrophila group (Bs+Ah), and the three experimental groups were intraperitoneally injected with 1×10⁵ CFU/fish A. hydrophila, and B. subtilis diet contained 1×10⁷ CFU/g for a trial of 56 days. The results showed that two groups fed with B. subtilis had higher weight gain rate and special growth rate compared with the Ah group (P<0.05). B. subtilis significantly decreased liver lipid droplet size and the hepatic lipid content at day 28 (P<0.05), increased the content of serum cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and reduced activities of aspartate aminotransferaseand alanine aminotransferase. B. subtilis downregulated the expression of acetyl-CoA carboxylase alpha and upregulated the expression of lipoprotein lipase and adipose triglyceride lipase on day 28. B. subtilis enhanced superoxide dismutase, catalase, glutathione and total antioxidant capacity, and diminished malondialdehyde and hydrogen peroxide. In conclusion, probiotic B. subtilis supplementation can promote growth, enhance the antioxidant function, reduce the liver damage caused by infection of A. hydrophila, regulate the hepatic lipid metabolism, and reduce the hepatic lipid accumulation in grass carp.