Abstract: Objective To measure the LD50 of ethanol extracts of Eupatorium adenophorum Spreng. Methods Kunming mice were given the ethanol extracts of Eupatorium adenophorum Spreng by intragastric administration. Through the pre experiment, to find out the 0% and 100% lethal dose (Dmin , Dmax) of ethanol extracts of Eupatorium adenophorum Spreng, as a basis for the formal test, to calculate the group distance of experimental group. The detailed reactions and death Results of mice were observed and recorded through the formal test, LD50 was calculated with probit weighted regression method (Bliss) by the SPSS 17.0 statistics software. Results LD50 of Eupatorium adenophorum Spreng was 126.3 g·kg^-1, and 95% confidence interval was 107.8~146.6 g·kg^-1. Conclusion The toxicity of Eupatorium adenophorum Spreng is higher.

Key words: Eupatorium adenophorum Spreng, mice, intragastric administration, LD50