Two hundred and fifty-five weaner piglets [(35?1) days of age, Duroc譒andrace譟orkshire] were used to study the effects of Enterococcus faecium on the growth performance, intestinal flora and immune function. These piglets were randomly allocated into 5 groups with 3 replicates per group and 17 piglets per replicate in a complete randomized design. The control group was fed a basal diet only, antibiotic group was fed the basal diet+8 mg/kg flavomycin and 90 mg/kg arsanilic, and the three Enterococcus faecium groups were fed the basal diet+100, 300, 500 mg/kg Enterococcus faecium, respectively. The experiment lasted for 35 days. The results showed as follows: 1)compared with the control group, average daily gain (ADG), average daily feed intake (ADFI) and feed/gain (F/G) had no significant difference among 5 groups (P>0.05); the addition of 100 and 300 mg/kg Enterococcus faecium tended to increase ADFI (P>0.05); the supplementation of 500 mg/kg Enterococcus faecium tended to reduce F/G (P>0.05). Compared with the antibiotic group, there were no significant differences in ADG, ADFI and F/G when piglets fed diets with Enterococcus faecium (P>0.05). 2) Compared with the control group, diets supplemented with 300 and 500 mg/kg Enterococcus faecium significantly increased the number of Lactobacillus in caecum (P<0.05), and there was no significant difference between the Enterococcus faecium group and the antibiotic group (P>0.05). Compared with the control group, the diet supplemented with 500 mg/kg Enterococcus faecium significantly reduced the number of Escherichia coli in colon (P<0.05), and the supplementation of 300 and 500 mg/kg Enterococcus faecium significantly increased the number of Lactobacillus in colon (P<0.05). Compared with the antibiotic group, the supplementation of 300 and 500 mg/kg Enterococcus faecium significantly increased the number of Lactobacillus in colon (P<0.05). 3) Compared with the control group, the supplementation of 300 mg/kg Enterococcus faecium significantly increased spleen weight and spleen index of piglets (P<0.05). The addition of 300 and 500 mg/kg Enterococcus faecium in the diets significantly increased spleen weight compared with the antibiotic group (P<0.05). 4) Compared with the control group, adding 300 and 500 mg/kg Enterococcus faecium significantly improved the number of lymphocyte and lymphocyte rate in blood of piglets (P<0.05); the supplemetation of Enterococcus faecium significantly increased the content of immunoglobulin G (IgG) in serum of piglets (P<0.05); the supplementation of 300 and 500 mg/kg Enterococcus faecium significantly increased the content of immunoglobulin M (IgM) in serum of piglets (P<0.05). Compared with the antibiotic group, the addition of 300 and 500 mg/kg Enterococcus faecium in the diets significantly improved lymphocyte rate in blood and the content of IgM in serum of piglets (P<0.05), and the supplemetation of Enterococcus faecium significantly increased the content of IgG in serum of piglets (P<0.05). It is concluded that Enterococcus faecium will be an ideal feed additive to improve the growth performance, regulate intestinal microflora balance and the immune function in piglets and the optimum supplemental level of Enterococcus faecium is 500 mg/kg.