Eight commercial livestock microbial agents were selected for the evaluation of biological toxicity. The general physical, chemical and microbial analyses of these microbial agents were performed and the acute toxicity of mice, aquatic living organisms and the germinated inhibition of vegetable seeds by these microbial agents were also estimated for the evaluation of biological toxicity. The results have shown that all livestock microbial agents have no pathogenic Salmonella and Staphylococcus aureus been detected. However, the acute biological toxicity test of water extractant of these microbial agents indicated that microbial agent A, B, C, D and M appeared various toxicity to the mice. The dosage of LC50 (48 hr) to the mice was 3 mg/ml for microbial agent A (150 mg/kg mouse, high toxicity), 90 mg/ml for microbial agent B (4.5 g/kg mouse, low-medium toxicity), 92 mg/ml for microbial agent C (4.6 g/kg mouse, low-medium toxicity), 118 mg/ml for microbial agent D (5.9 g/kg mouse, low toxicity) and nontoxicity for microbial agent M, respectively. In addition, the dosage of LC50 to aquatic organisms Daphina similis and Lemna minor, was < 0.01 mg/ml and 0.13 mg/ml for microbial agent A, 1.73 mg/ml and 10 mg/ml for microbial B, 3 mg/ml and > 20 mg/ml for microbial C, 0.56 mg/ml and 14 mg/ml for microbial agent D, respectively. All microbial agents also show various inhibitory effects to the seed germination and root extension of vegetable crops. The study has demonstrated that the biological toxicity of livestock microbial agents was following such order: microbial A > B, C > D > M. The animal has shown more sensitive than plant to the microbial agents.