Abstract: To investigate the effects of Lactobacillus johnsonii CIP103620 on the growth performance and lipid metabolism of Monopterus albus, 180 M. albus individuals were randomly divided into a control group (CL, basic feed), a fermentation group (JF, 1×10⁷ CFU/g L. johnsonii fermentation feed), and a spraying group (JS, surface spraying with the same amount of live bacteria feed). The feeding experiment lasted for 8 weeks. Results showed that compared with the control group, the final weight, weight gain rate and specific growth rate were significantly increased in both the JF group and JS group (P<0.05), with a more pronounced effect observed in the JS group. Both treatment groups significantly increased the crude fat content in whole fish and muscle (P<0.05) and reduced the lipid deposition in the liver (P<0.05). In addition, both groups significantly reduced the levels of serum triglycerides, total cholesterol, low-density lipoprotein cholesterol, and non-esterified free fatty acids (P<0.05), and increased the activities of hepatic lipase, lipoprotein lipase, and total lipase (P<0.05). Gene expression analysis revealed that the expression of lipolysis-related genes (cpt1, lpl, hsl, atgls) and some lipogenic genes (acc1, fas) was significantly up-regulated in the JS group, while the expression of acc2 gene was down-regulated (P<0.05). The up-regulation of lipolysis-related gene expression in the JF group was weaker. Therefore, L. johnsonii may effectively promote the growth of M. albus and improve lipid metabolism homeostasis by enhancing lipid catabolism in the liver and regulating the expression of related genes. Comprehensive analysis showed that the live bacteria spraying treatment had a more significant effect on promoting growth and regulating lipid metabolism, and was a more suitable application method for probiotics.