The herbicidal activities of methanol extracts of Aralia armata (Wall.) Seem., Phytolacca americana L.,Dipsacus chinensis Batal.,Datura metel L.,Pterocarya stinoptera C. DC. and Cirsium japonicum DC. were tested against the invasive weeds,Mikaina micrantha,Bidens pilosa Lin., Conyza bonariensis (L.) Cronq, Pistia stratiotes L.and Alternanthera philoxcroides (Mart.) Griseb.. Results showed that after 7 d, at the concentration of 5.000 mg/mL, the root inhibition rates of methanol extracts of D.chinensis on M.micrantha, B.pilosa，C.bonariensis and P.stratiotes were 90.05%, 83.71%, 92.68%, 100% respectively, while the inhibition rates of A.armata on them were 79.21%, 81.17%, 88.09%,100% respectively. Methanol extracts of A.armata exhibited significant inhibition activity on P.stratiotes,C.bonariensis and B.pilosa. The IC50 values were 0.342 4, 0.409 0 and 0.696 6 mg/mL respectively. Methanol extracts of D.chinensis and P.americana showed high root inhibition effect to M.micrantha,with the IC50 values low to 0.721 0 and 0.716 7 mg/mL respectively.