To investigate the effects of different kinds of acidifier on intestinal development, digestive enzyme activities and microbiota number of broiler chickens, a total of 840 one-day-old male Arbor Acres (AA) broiler chicks were randomly allocated into 7 treatments with 6 replicates per group and 20 broilers per replicate. The control group was fed a basal diet, and test groups were fed the basal diet supplemented with phosphoric acid (PA), coated phosphoric acid (CPA), phosphoric acid+lactic acid (PLA), fumaric acid (FUA), formic acid (FA) and citric acid (CA), respectively (the H⁺ concentration was 9.18 mmol/kg). The experiment lasted for 42 days. The results showed as follows:1) dietary supplemented with PA significantly increased the activities of trypsin and chymotrypsin in small intestine at 21 and 42 days of age (P<0.05). 2) Dietary supplemented with CPA significantly increased the chymotrypsin activity in small intestine (P<0.05). 3) Dietary supplemented with PLA significantly increased trypsin activity in small intestine at 42 days of age (P<0.05). 4) Dietary supplemented with FUA significantly increased the activities of trypsin and chymotrypsin in the small intestine at 42 days of age (P<0.05), but significantly reduced the number of Escherichia coli in cecal at 42 days of age (P<0.05). 5) Dietary supplemented with FA significantly increased the trypsin activity in the small intestine at 21 and 42 days of age (P<0.05), but significantly reduced the number of Escherichia coli in cecal at 42 days of age (P<0.05). 6) Dietary supplemented with CA significantly increased the activities of trypsin and chymotrypsin in the small intestine at 21 and 42 days of age (P<0.05), but significantly reduced the number of Escherichia coli in cecal at 42 days of age (P<0.05). In conclusion, PA, CPA and PLA can increase small intestinal digestive enzyme activities; FUA, FA and CA can improve small intestinal digestive enzyme activities, and decrease harmful cecal microbiota number of broilers.