Abstract: Objective To understand the appropriate concentrations of 2, 3, 5-triphenyltetrazolium chloride (TTC) under which bacteria begun to be inhibited or were completely inhibited in enrichment broth. Methods The liquors containing Staphylococcus aureus, Shigella flexneri, Salmonella, Escherichia coli, Proteus vulgaris,Vibrio parahaemolyticus with different concentrations were added into nutrient broth containing 1.0 mg/ml agar (Vibrio parahaemolyticus was added into 3% alkaline peptone water) and the TTC concentrations when bacteria began to be inhibited or were completely inhibited were recorded. Results When bacterium liquors concentration was 30-300 cfu/ml, the TTC concentrations when Staphylococcus aureus, Shigella flexneri, Salmonella, Escherichia coli, Proteus vulgaris, Vibrio parahaemolyticus began to be inhibited were 0.02, 0.1, 0.2, 0.6, 0.6 and 0.1 mg/ml respectively, and the TTC concentrations when the bacteria were completely inhibited were 0.1, 0.7, 0.5, 2.0, 2.0 and 0.2 mg/ml respectively. Conclusion The detection rate of bacterium could be increased by adding 1.0 mg/ml agar and appropriate amount of TTC into enrichment broth and the amount of bacterium in the sample can be observed. The detection rate could be further increased by choosing the enrichment broths with different TTC concentrations