In order to investigate the detoxification of Lactobacillus plantarum BS22 on aflatoxin and its influence on gut microflora of broilers chicken, various amount of BS22 addition test with and without feeding were arranged. Test of 106, 107, 108 CFU/g amount of BS22 were added into the feedstuff with 50 μg of B1 (AFB1), and the AFB1 content was measured after day 0, 15 and 30 day. The results showed that AFB 1 content in feeding group was significantly decreased after BS22 addition. While, it increased with the storage time of feedstuff at the same amount of addition. The test for feeding broilers, last for 28 days, was set into three groups, they were group I, basal diet (control group); group II, basal diet plus 50 μg/kg AFB1; group III, basal diet plus 50 μg/kg AFB1 and Lactobacillus plantarum BS22 (1.0×108 CFU/g feed). Structure of bacterial communities and contents in glandular stomach, duodenum, jejunum, ileum, cecum and mucosa were compared using PCR–DGGE approach at the fourth week. The results showed that Shannon-Wiener index (H'), Evenness (EH) and Richness (S) in group III were higher than that in group II and group I for those contents in all gastrointestinal except for in ileum. Clustering diagram showed that group II and group I clustered together, group III, however, was separated in gastrointestinal except for in glandular stomach and in cecum. For those in mucosa, the Shannon–Wiener index (H') and Evenness (EH) in group II were higher than that in group III and group I in mucosa except for in jejunum and cecum. The Shannon–Wiener index (H') in group III and group I were the same or similar. Cluster analysis showed that group III and group I clustered together, while group II was separated in mucosa except for in ileum and cecum. In general, aflatoxin B1 took little effect on the flora in intestinal contents, but had greater impact on mucosal flora. Lactobacillus plantarum BS22 could adjust the imbalance of mucosal flora caused by aflatoxin B1.