Abstract:The reproductive characteristics of Eupatorium odoratum population in three typical communities, such as E. odoratum community (dominancy community), Vitex negundo-E. odoratum community (mixed community), and Neyraudia reynaudiana -Microstegium vegans community (concomitant community), were studied in karst rocky mountain in Guangxi. The results showed that the number of capitulum of E. odoratum in 1 square meter ranged from 520 to 3281, and seed yield from 12941 to 74386 grains m-2, each capitulum produced 22 to 25 seeds and the 1000-seed-weight ranged from 0.17 to 0.19 g. The number of capitulum and seed yield per individual in mixed community were significantly different from those in concomitant community, but there were not significant difference between dominant community and two another communities. There was a positive correlation between individual seed yield and plant height, as well as biomass. Seed yield in unit area was positively correlated with the number of flowering plants and capitulum, but was weakly correlated with coverage. In the three communities in arid karst rocky mountain, E. odoratum could produce a large number and light seeds, it indicated that E. odoratum had strong reproductive capacity and displayed strong invasive, and it also could choose the corresponding reproductive strategy according to the environment change, so that it could adapt to environment at large scale.