Abstract: Objective The acute toxicity of water extract of Sophorae tonkinensis Radix et Rhizome on mice was researched to determine the correlation of "toxicity-syndrome". Methods The sample water extract of Sophorae tonkinensis Radix et Rhizome was administrated to KM mice of the throat excess- heat syndrome models. The LD50 of Sophorae tonkinensis Radix et Rhizome was tested by the classical Methods of acute toxicity. The acute toxic symptoms were observed, the accumulated death number and the weight-changes of live mice were recorded. Results The LD50 and its 95% confidence limits of water extract of Sophorae tonkinensis Radix et Rhizome was 20.63(17.94～23.92)g·kg^-1 in mice. Restlessness, breathlessness and convulsion were the main acute toxic symptoms. Conclusion The acute toxicity of water extract of Sophorae tonkinensis Radix et Rhizome on throat excess-heat syndrome mouse model in mice was significantly less than normal animals. The onset time of toxic symptoms was delayed and relieved, the LD50 value was increased.

Key words: Sophorae tonkinensise Radix et Rhizome, water extract, throat excess-heat, acute toxicity