ABSTRACT Goose fatty liver is a delicious food product and the overfeeding will cause the abnormal physiology of the geese. The objective of this study was to investigate the effect of supplementation with hydrated sodium calcium aluminosilicate (HSCAS) on the fatty liver, ileal and cecal microbiota of Landes geese during overfeeding. Sixty 70-day-old Landes geese (body weight= 3.0 ± 0.05 kg) were randomly divided into three groups, two of which were overfed with whole corn supplemented with or without HSCAS for 20 days when the fatty liver reaches to the maximum size and the negative control group was ad libitum access to the corn basal diet. The intestinal contents of the ileum and cecum from three geese per group were used for high-throughput sequencing. As a result of this study, the HSCAS-treatment led to an increase in relative liver weight (p<0.05) of geese compared with the overfeeding control group. The richness and diversity of the bacterial communities decreased in the ileum and ceca after overfeeding. Overfeeding increased the relative abundance of Firmicutes, especially Lactobacillus, in ileal samples. HSCAS supplementation increased the relative abundance of Lactobacillus, and decreased the relative abundance of Actinobacillus in the ileum and the relative abundance of Erysipelotrichi, Bacteroides and Escherichia in the ceca. Bacterial richness indicators were also increased in samples from ileum and ceca after HSCAS supplementation. In conclusion, dietary HSCAS supplementation promoted liver performance in overfed Landes geese. HSCAS treatment had a beneficial effect on the intestinal microbiota composition in geese during the overfeeding.