Abstract: Eupatorium adenophorum is a weed with strong invisibiliteedling can produce certain substances during its cotyledons growing.These substances can inhibit the growthing seeding of Hordeum vulqane and Zea mays,including the seeding height,root length and leaf length.The inhibition effect is up to 32%,13% and 43%,to Hordeum vulgare,respectively,and 45%,35%,82% to Zea mays.They also inhibit growth of Eupatorium adenophorum seedling’s root but promote growth of its leaves and stem within certain concentration.Eupatorium adenophorum’s root secretion may play an important role in the process of spreading and occupying new ecological niche.