The in vitro antibacterial activity of ethanol extract from Bauhinia championii (Benth.) Benth growing in Guangxi, China, was evaluated against S. mutans using twofold agar dilution method. The present study showed that minimal inhibitory concentration was 12.5 mg/mL and there have significant inhibitory activity of adherence and acidogenicity against S. mutans when the extract concentration was greater than or equal to 3.13 mg/mL. These results indicate that Bauhinia championii (Benth.). Benth extract can significantly inhibit the growth, adherence and acidogenicity of S. mutans and might be used in the area of dental caries prevention and treatment in the future.