Abstract: A total of 360 Nile tilapia at an average initial body weight of 3.9g were randomly allocated to 4 treatments,each of which had three replicates of 30 fish/tank and used to investigate the effects of copper-bearing montmorillonite(Cu-MMT) on intestinal microflora and digestive function.The fish received the same basal diet and Cu-MMT was added to the basal diet at 0,0.10%,0.15% and 0.20%,respectively.As compared with the control,supplementation with Cu-MMT significantly reduced the total intestinal aerobic bacterial counts,affected the composition of intestinal microflora with a tendency of Aeromonas,Pseudomonas,Flavobacterium,Acinetobacter,Alcaligence,Enterobacteriaceae and Vibrio decreasing.Addition of 0.10%,0.15% and 0.20% Cu-MMT significantly improved the apparent digestibility coefficients of dry matter,crude protein and crude lipid and by 6.43%,8.47% and 8.83%,5.63%,6.24% and 6.91%,4.62%、5.65% and 5.98%,respectively(pppp<0.05).Cu-MMT also increased villus and microvillus heights at different sites of the intestine.The results suggest that Cu-MMT can inhibit effectively the growth and proliferation of pathogenic bacteria in the intestinal tract,which can protect intestinal mucosa from invasion of pathogenic bacterium and toxins,resulting in a positive effect on the health and function of intestinal mucosa,and then promote the digestion and absorption of dietary nutrition.