This experiment was conducted to investigate the effects of dietary different levels of Enteromorpha prolifera polysaccharide on intestinal digestive enzyme activity, microbial number and nutrient apparent utilization of broilers. A total of 840 one-day-old Arbor Acres (AA) broilers were randomly divided into 7 groups with 6 replicates in each group and 20 broilers in each replicate. Broilers in the control group (group 1) were fed a corn-soybean basal diet, and the others were fed the basal diets supplemented with 0.02%, 0.05%, 0.10, 0.20, 0.40, and 0.80 Enteromorpha prolifera polysaccharide, respectively. The experiment last for 42 days. The results showed as follows:1) the jejunal contents chymotrypsin activity of group 5 was significantly higher than that of groups 1, 2, 3 and 7 (P<0.01); the jejunal contents chymotrypsin activity of groups 4 and 6 was significantly higher than that of group 1 (P<0.01), and significantly higher than that of group 2 (P<0.05). The jejunal contents trypsin activity of groups 4, 5 and 6 was significantly higher than that of groups 1, 2, 3 and 7 (P<0.05 or P<0.01). The jejunal contents lipase activity of groups 3 to 6 was significantly higher than that of group 1 (P<0.05 or P<0.01). There was no significant difference on jejunal contents amylase activity among all groups (P>0.05). 2) The ileum contents Lactobacillus number of group 6 was significantly higher than that of group 1 (P<0.01). There were no significant difference on numbers of Escherichia coli and Bifidobacterium in ileum contents among all groups (P>0.05). 3) During 1 to 21 days of age, the crude protein apparent utilization of group 6 was significantly higher than that of group 1 (P<0.05), the calcium apparent utilization of groups 1 to 6 was significantly higher than that of group 7 (P<0.05). There were no significant difference on total phosphorus apparent utilization among all groups (P>0.05). During 22 to 42 days of age, the ether extract apparent utilization of groups 6 and 7 was significantly higher than that of groups 1 and 2 (P<0.05). There were no significant difference on apparent utilizations of crude protein, calcium and total phosphorus among all groups (P>0.05). In conclusion, dietary Enteromorpha prolifera polysaccharide can improve the activities of chymotrypsin and trypsin, Lactobacillus number and nutrient apparent utilization. The suitable supplemental level of Enteromorpha prolifera polysaccharide in diet of broilers is 0.10% to 0.40%.