Four anaerobic strains were isolated from the rumen of the cattle which no specific toxic symptoms were seen when Leucaena was fed in Weizhou island Beihai city, Guangxi Province, China. All of these strains (BR-1, BR-2, BR-5 and BR-7) possess degradative activities to toxic mimosine, 3-hydroxy-4 (1H) -pyridone (3, 4-DHP) and 2, 3-dihydroxypyridine (2, 3DHP) from Leucaena, that were confirmed by analysis of HPLC. Pure and mixed cultures of these four strains in vitro degraded 44-59% of mimosine, 30-47% of 3, 4 DHP, and 58-60% of 2, 3 DHP respectively in 3 days. Strains of Both BR-1 and BR-2 were almost identical and were characterized as Lactobacillus, may be a new species. Strains of BR-5 and BR-7 were characterized as Streptococcus bovis and Clostridium sporogenes respectively. It has not yet been reported that these Gram positive facultatively and obligately anaerobic bacteria were able to degrade mimosine, 3, 4 DHP and 2, 3 DHP. These detoxic bacteria were existing in the rumen microflora of cattle in Weizhou island, protecting therefore their hosts animal from Leucaena toxicity.