Objective To determine the antibacterial activity of six kinds of natural herbs in Yunnan on normal oral predominant bacteria in vitro. Methods Agar dilution method, the antimicrobial susceptibility testing of anaerobes which was recommended by National Committee for Clinical Laboratory Standard（NCCLs）, was used to determine the antimicrobial susceptibility of herbs to 21 kinds of oral model strains and clinical isolates. The results were expressed by minimum inhibitory concentration（MIC）. Results All six kinds of herbs were effective to the oral predominant bacteria. For the ten kinds of cariogenic bacteria, the MIC of caesalpinia sappan lignum was between 5-10 mg·mL-1, and the MIC of other herbs was above 20 mg·mL-1. For the eleven kinds of predominant bacteria which normally involved in pulp periapical disease and periodontitis, the MIC of caesalpinia sappan lignum was below 0.062 5 mg·mL-1, and the MIC of the terminalia chebula retz was between 10-20 mg·mL-1, and the others were above 20 mg·mL-1. Conclusion The six kinds of herbs in Yunnan could be used in treatment or prevention of oral bacterial diseases.
