This experiment was conducted to investigate the effects of diet adding β-glucan on growth performance, immune function and intestinal micro environment of broilers. A total of 672 one-day-old Arbor Acres (AA) broilers were randomly allocated to 4 groups with 14 replicates per group and 12 chickens per replicate. The control group was fed a basal diet, while the experimental groups were fed the basal diet supplemented with 100, 150 and 200 g/t β-glucan, respectively. The experiment lasted for 42 days. The results showed as following: 1) the weight gain of broilers aged from 1 to 21 days in 150 g/t groups was significantly higher than that in control group (P<0.05). 2) The serum immunoglobulin content of broilers in 150 g/t group was higher than that in control group (P>0.05). 3) At 21 days of age, the caecal Lactobacillus number of broilers in 150 g/t group was significantly higher than that in control group (P<0.05), while the number of Salmonella in jejunum and ileum was significantly lower than that in control group (P<0.05). At 42 days of age, the caecal Salmonella number of broilers in 150 and 200 g/t group was significantly lower than that in control group and 100 g/t group (P<0.05). 4) The villus height to crypt depth ratio in the jejunum of broilers was significantly influenced by dietary β-glucan supplementation (P<0.05). In conclusion, moderate β-glucan supplementation can improve the commercial body weight, growth performance and the number of Lactobacillus in caecum, while reduce the number of Salmonella in jejunum, ileum and caecum.