In order to explore the effects of different microbial preparations on the growth,body index and intestinal tissue structure of Micropterus salmoides,different concentrations of Clostridium butyricum[0(group A,CK),0.25%(group B),0.5%(group C),1%(group D)Clostridium butyricum(5×108cfu·g-1)],0.2%yeast prod-ucts(group E)and their mixture(0.25%Clostridium butyricum+0.2%yeast products,group F)were added to the commercial compound feed for a two-stage breeding experiment for 17 weeks.The results showed that:in the first stage(14 weeks),except for adding 0.2%yeast products(group E),the growth performance of Micropterus salmo-ides was significantly improved compared with the control group,and the effect of adding 0.5%Clostridium butyri-cum was the best.In the second stage(17 weeks),the final mean weight and final body length of 0.5%Clostridium butyricum(group C)and 0.25%Clostridium butyricum+0.2%yeast products(group F)were significantly higher than those of the control group A.There were no significant differences in the fullness,visceral-body ratio index,length of intestinal villus and muscle layer thickness among the three groups.However,compared with the control group(group A),the indexes of adding 0.5%Clostridium butyricum(group C)had an increasing tendency,and the indexes of adding 0.25%Clostridium butyricum+0.2%yeast products(group F)had a decreasing tendency.The results showed that under the experimental conditions,the addition of 0.5%Clostridium butyricum to the commer-cial compound feed had the best effect on the growth and improvement of intestinal health of Micropterus salmoides.