| To investigate the potential ecological damage effects of alien invasive species Gomphrena celosioides, allelopathic effects of water extracts of different plant organs on seed germination and seedling growth of three cultivated plants seeds are tested. Results showed that in general, the lower concentration of flower and leaf water extracts decreased seed germination rates and root growth of Raphanus sativus, Brassica juncea, and B. parachinensis, even researched a very significant level. The higher the concentration of water extracts, the stronger the inhibition effect was. Meanwhile, the lower concentration extracts increased the stem (bud) length, but the effects decreased as the concentration enhancing, some significant inhibition effects occurred while the extracts concentration reached a higher levels. Comparing the total effect index, we knwe that the effects of leaf water extracts was stronger than that of flower water extracts. The inhibition order of allelopathic effects of leaf water extracts on cultivated species was B.juncea> R.sativus> B. parachinensis, and for flower water extracts, the order was R.sativus > B. juncea > B. parachinensis. As an alien invasive plant, G.celosioides had a stronger allelopathic effect on cultivated plants, and some prevention and cure countermeasures should be taken.