Abstract: For study on the harm of Eupatorium catarium to native species and its invasive mechanism, it were conducted the allelopathy of ultrasonic extraction from alien invasive plant Eupatorium catarium on seed germination and seedling growth in Mung bean, Radish, Brassica junceavar foliosa, Eleusin indica.. The results showed the high concentrations of ultrasound extraction from Eupatorium catarium could significantly inhibits germination ratio in small seeds and the growth of plants root. 0.2%-0.4% ultrasonic extract of Eupatorium catarium can significantly promotes the growth of plant shoots and improve the content of chlorophyll a in young leaves.