Abstract: To explore the allelopathic effect of Eupatorium catarium Veldkamp as green manure on common weeds in the field, five plants(Eupatorium odoratum L., Mimosa pudica L., Echinochloa crusgalli (L.)Beauv, Bidens pilosa L. and Abutilon theophrasti Medic) were selected as receivers in pot experiment and the allelochemical donator was Eupatorium catarium Veldkamp. The rate of emergence, stem length, aboveground biomass and underground biomass of receiver plants were measured. The results indicated that: (1) Eupatorium catarium Veldkamp had strong inhibition to the germination of weeds, of which it was obvious on Echinochloa crusgalli (L.)Beauv and Eupatorium odoratum L.. The germination of both plants was totally inhibited under low application dose. (2) Relatively weak inhibitory action was shown to weed seedlings and even the growth of some plants was promoted. Therefore, our experiments confirmed that the time during which the weed could be effectively suppressed was before germination; meanwhile, the control object should be sensitive to allelopathy.