Abstract: The effects of dietary Lactobacillus acidophilus on growth performance, digestive enzyme activities, premunition and related enzyme gene mRNA expression of Epinephelus coiodes were assessed in the current study. Seven hundred and twenty healthy fish with an average body weight of (5.60±0.05) g were randomly divided into 8 groups with 3 replicates per group and 30 fish per replicate. The fish were fed a basal diet and an experimental diet that were supplemented with L. acidophilus at the percentage of 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2% for 8 weeks, respecti-vely. The WGR and SGR increased first and then decreased with increased L. acidophilus, but they were significantly higher than those of the control group (P<0.05). The FCR reached the lowest value in 0.6% group that was signifi-cantly lower than other group (P<0.05). However, the PER level showed an opposite trend to the FCR. The activities of TRY and AMY in the liver and intestine tended to increase first and decrease thereafter. The liver TRY and AMY mRNA level of the experimental group were significantly higher than those in the control group (P<0.05). Among them, liver amylase and protease activity reached the maximum level at 0.6%, and intestinal protease and amylase activities reached the maximum level at 0.2% and 0.4%, respectively. The fish survival rate significantly increased with the increased Vibrio harvey for 7 days (P<0.05). These results reveal that 0.42% Lactobacillus acidophilus (0.72×10⁸ cfu/mL) in the feed could significantly promote the growth and increase the digestive enzyme activity and disease resis-tance for juvenile grouper.