A feeding study was performed to investigate possible performance enhancing effects of the rare earth-chitosan chelate (RECC) on intestinal structure of Carassius auratus L. Three hundred and sixty individuals (about 5.0 g) were allotted to four dietary treatments: a control group and three RECC-treated groups. RECC-treated groups were supplemented with 800 mg,1 600 mg and 2 400 mg of RECC per kg feed respectively. Each group had three duplicates. The whole feeding period lasted for sixty days.Resultsare as follows: RECC added in diet promoted the development of intestine. It was found that RECC-treated groups had higher numbers of plicamucosa than the control group,and plicamucosas became longer and narrower. Compared with the control group,the 0.08% RECC group had a greater number of plicamucosa (P<0.05),a lower width of policamucosa (P<0.05),and a higher number of goblet cells (P<0.05); the 0.16% RECC group had a greater number of goblet cell (P<0.01). Scanning electron microscope observation showed that microvilli in RECC-treated groups were more uniform and denser than the control group.