This experiment was conducted to study the effects of Clostridium butyricum on growth performance,serum biochemical parameters and rumen environment of mutton sheep.30 Duhu crossbred sheep were randomly divided into 2 groups with 3 replicates in each group and 5 sheep in each replicate.The control group was fed with basal diet,and the experimental group was fed with basal diet supplemented with 200 mg/kg Clostridium butyricum.The experiment was 60 days.The results showed that the average daily gain(ADG)of the experimental group was significantly higher than that of the control group(P<0.05),and the feed conversion ratio was significantly lower than that of the control group(P<0.05).The ratio of serum albumin to globulin(ALB/GLB)in the experimental group was significantly higher than that in the control group(P<0.05).There was no significant difference in the content of volatile fatty acids between the two groups(P>0.05),but the activity of amylase in the rumen fluid of the experimental group was significantly lower than that of the control group(P<0.05).In conclusion,dietary supplementation of Clostridium butyricum improved the performance of mutton sheep,but had no significant effect on rumen environment.