【Background】Alternanthera philoxeroides (Mart.) Griseb, an invasive exotic weed, is difficult to control. Using allelopathy as a potential control method could provide a solution. 【Method】Allelopathy of waterbased extracts from different organs of nine plant species, Macleaya cordata (Willd.) R.Br, Momordica charantia Linn., Cinnamomum camphora, Cryptomeria fortunei Hooibrenk ex Otto et Dietr, Pteris multifida Poir, Citrus reticulate Blanco, Nerium oleander L., Allium cepa Linn., Allium sativum L., was assessed on the alligator weed, Alternanthera philoxeroides. 【Result】The extracts from leaves of Macleaya cordata, pulp and seed of Momordica charantia, P.multifida appeared to significantly affect Alternanthera philoxeroides. The number of leaves and nodes of Alternanthera philoxeroides decreased, plant height and biomass of Alternanthera philoxeroides was reduced after treated with waterbased extracts from leaves of Macleaya cordata, both pulp and seed of Momordica charantia, P.multifida. 【Conclusion and significance】The research provides options to develop control methods against Alternanthera philoxeroides via the use of allelopathy.