Abstract: In this study,the influences on cherry valley ducks by B.coagulans were investigated at the growth performances,serum biochemical indexes,activities of digestive enzymes in the duodenal contents,and the cecum microbiome.750one-day-old ducklings were allocated into 5groups.Each group had 5replicates,and there were 30 ducklings in each replicate.GroupⅠ was fed with based diet and acted as the negative control.GroupⅡ was supplemented with 300 mg 10%zinc bacitracin per kg of the feed.GroupⅢ,ⅣandⅤ were supplemented with 100,200 and 300mg B.coagulans with the microbial count was 1.0×109 CFU·g-1 per kg of the feed,respectively.The whole experiment lasted for 42 days.The results showed that the feed/weight gain ratio(F/G)in GroupⅡ-Ⅴ were significantly lower than that in GroupⅠ(P<0.05)from Day 1to Day 21.Compared to GroupⅠ,the average daily weight gain(ADG)in GroupⅣ from Day 1to Day 42 were significantly higher(P<0.01),but F/G were significantly lower(P<0.01).The ADG in GroupⅤ was significantly higher than that in GroupⅠ during the same period.The differences of alkaline phosphatase(ALP)activity and albumin(ALB)content among groups were not significantly(P>0.05)on Day 21.But on Day 42,both of them were significantly higher in GroupⅣ than those in GroupⅠ(P<0.05).The amylase activities in GroupⅣandⅤ were significantly higher than that in GroupⅠ(P<0.05)on Day 21.The trypsines in GroupⅢ-Ⅴ were higher than that in GroupⅠ(P<0.05)on Day 42.The amount of Lactobacillus spp.in cecum of ducklings in GroupⅤ was significantly higher than GroupⅠandⅡ(P<0.05)on Day 21.On Day 42,this amount in Group Ⅳ was significantly higher than that in GroupⅠ(P<0.05).On both of Day 21 and 42,the quantity of Escherichia coli in GroupⅤ was significantly higher than that in GroupⅠ(P<0.05).Therefore,we came to a conclusion that the feeding with 200 to 300mg per kg of the feed B.coagulans resulted in the decrease of F/G and the quantity of E.coli in cerum,the increase of ADG,ALP activity,ALB content,trypsin activity,and the amount of Lactobacillus spp.,which helped to improve the environment of microecology.