[Background] Eupatorium catarium Veldkamp is an invasive exotic weed in south China, registered from the coast of Hainan, Fujian, Guangdong, and other coastal provinces. Its presence in most orchards, grassland, and farmland caused great harm to the local agricultural production.[Method] Allelopathic effect of watery extract (0.010 g·mL^-1, 0.025 g·mL^-1, 0.050 g·mL^-1) from E. catarium was tested on four crops, watermelon Citrullus lanatus, rice Oryza sativa, radish Raphanus sativus and bell pepper Capsicum annuum under laboratory conditions.[Result] The results showed that increasing concentrations of E. catarium had significant increasing allelopathic inhibition on seed germination and seedling growth of the four plants. At the extract concentration of 0.050 g·mL^-1, the sensitivity rank of the four crops was:C. lanatus >R. sativus >O. sativa >C. annuum.[Conclusion and significance] Understanding the allelopathic effect of E. catarium on different crops can provide scientific basis for prevention and control of this weed.