A total of 750 37-week-old black-feathered muscovy ducks of laying period were randomly and evenly divided into 5 groups with 5 replicates in each group. Ducks in the control group were fed the basal diet, and ducks in the experimental groups were fed the diet supplemented with 2%, 4%, 6% and 8% fermented feed, respectively. The pre-trial period was 7 days, and the trial period was 37 days. The effects of fermented feed on production performance, body fat content, fat metabolism-related gene expression and cecal microbiota of laying muscovy ducks were explored. The results showed that there were no statistically significance in egg production rate, average egg mass, daily egg mass and feed-to-egg ratio between the different levels of fermented feed groups(P>0.05), but addition of 4%, 6% and 8% fermented feed to the diet significantly(P<0.05) reduced broken(soft) rate of the laying muscovy ducks. There were no statistically significance in fat contents in liver, breast muscle and leg muscle of ducks with different levels of fermented feed(P>0.05). Compared with the control group, FAS and LPL genes expression in the liver of the ducks within the 2% and 4% fermented feed groups and PPAR-γ gene expression in the liver of the duck within the 8% fermented feed group were significantly higher than those within the control group(P<0.05); ATGL gene expression in the abdominal fat of the ducks within the 4%, 6% and 8% fermented feed groups was significantly lower than that within the control group(P<0.05); and PPAR-γ gene expression in abdominal fat tended to increase(P=0.07). Sobs index of the 4% fermented feed group was significantly higher than that of the 6% group(P<0.05), and Shannon index of the 4% fermented feed group was significantly higher than that of other groups(P<0.05). 8% fermented feed significantly decreased the relative abundance of unclassified_o_Bacteroidales (P<0.05), and 4% fermented feed significantly increased the relative abundance of norank_f_Oscillospiraceae (P<0.05). In conclusion, fermented feed couldimprove broken(soft) rate and regulate the expression of fat synthesis-related genes. Meanwhile it could increase the diversity of intestinal microbiota and improve the structure of intestinal microbiota at the genus level. The optimal addition level of fermented feed in the diet was 4%.