Abstract: This study investigated the effects of high-fat diet (HFD) and naringin(Nar) supplementation on hepatic lipid metabolism and endoplasmic reticulum stress in largemouth bass (Micropterus salmoides). The aim was to provide a scientific basis for the application of plant extracts as aquaculture feed additives. The experiment used juvenile M. salmoides as the research subjects and set up six groups of feed, namely the control group (10.5% crude lipid), the high-fat group (18.5% crude lipid), the control group + 0.125% Nar, the high-fat group + 0.125% Nar, the control group + 0.25% Nar, and the high-fat group + 0.25% Nar. Each group had three replicates, and the experiment lasted for ten weeks. The results showed that in the HFD group, liver tissue was damaged and vacuolated, and oil O red staining revealed a large number of lipid droplets in the liver. The mRNA expression levels of lipid synthesis-related genes (scd1, fas, acca) and transcription factors SREBP1 and PPARγ were increased, while the mRNA expression levels of lipid decomposition-related genes (cpt1, cpt2, atgl, hsl) and transcription factor PPARα were decreased. The addition of naringin reduced the TG content in the liver and the mRNA expression levels of lipid synthesis-related genes, while increasing the mRNA expression levels of lipid decomposition-related genes. Additionally, compared with the control group, the transmission electron microscopy of the liver in the HFD group showed obvious swelling of the endoplasmic reticulum, and the mRNA levels of endoplasmic reticulum stress-related pathway genes (ire1, xbp1, elf2α, atf4, atf6, grp78) and the expression level of the endoplasmic reticulum stress marker protein GRP78 were increased. The addition of naringin alleviated the swelling of the endoplasmic reticulum in the liver and decreased the mRNA levels of endoplasmic reticulum stress-related pathway genes and the expression level of the endoplasmic reticulum stress marker protein GRP78. In conclusion, dietary naringin supplementation can alleviate HFD-induced hepatic lipid deposition and endoplasmic reticulum stress in M. salmoides. This provides a theoretical basis for the utilization of high-fat feed in aquaculture and offers reference into the addition of plant extracts in aquaculture feed.