[Objective] This study aimed to determine the optimum ethyl methane sulfonate（EMS） concentration for germination of tarary buckwheat seeds so as to lay a solid foundation for obtaining excellent traits of tarary buckwheat and breeding new varieties that meet the requirements by EMS mutation breeding. [Method] The seeds of Jinqiaomai No.4, a local tarary buckwheat variety [Fagopyrum tataricum（L.） Gaertn] in Shanxi Province, were used as the material. They were mutagenized by different concentrations（0.3%, 0.5%, 0.7%, 1.0%, 1.5%, 1.7%） of EMS for different times（4, 8, 12 h）. Then the germination rate and germination vigor were analyzed. [Result] With the increase of EMS mutagenic agent concentration, the germination vigor, relative germination vigor, germination rate and relative germination rate are all trended to be decreased. When the EMS concentrations ranged from 0.3%to 1.0%, there were no significant differences between treatment and control groups（P〉0.05）. When the EMS concentrations were 1.5% and 1.7%, significant differences were shown between treatment and control groups（P〈0.01）. The 4 and 8 h treatment of EMS all had no significant effects on germination rate and relative germination rate of Jinqiaomai No.4, but the 12 h treatment of EMS showed significant effects. Among the three treatment times, there were still no significant differences in germination vigor and relative germination vigor between treatment and control groups. [Conclusion] The optimum median lethal dose and treatment time of EMS for mutagenizing Jinqiaomai No.4 were 1.7% and 12 h, respectively.
