Abstract: The studies were conducted to evaluate the effects of the methanol, ethanol and distilled water extracts from the leaves of Coreopsis grandiflora Hogg. on the growth of Lagopsis supine (Steph.) IK.-Gal. and Echinochloa crusgalli (L.) Beauv. seedlings by the method of grinded plant tissue powders mixed with agar (PPA) at 0.625g?L-1 concentration. The results showed that the inhibitory activity of ethanol extracts was the highest, and its optimum extractive concentration was 100%. The leaves extracts obtained with 100% ethanol solution all displayed certain inhibitory activities on seedlings growth of E. crusgalli and L. supine at different concentrations and the EC50 on radicle/hypocotyl of L. supine and seminal root/coleoptile of E. crusgalli were 0.159g?L-1/0.595g?L-1and 0.489g?L-1/3.43g?L-1, respectively. Then, the extracts was further sequentially partitioned with petroleum ether, ethyl acetate and buthanol, respectively. Among obtained four fractions including water fraction, the petroleum ether fraction showed the highest inhibitory activities on the seedlings growth of lettuce, wheat, L. supine and E. crusgalli at 2g?L-1concentration. The results provide the evidence for further separation of herbicidal active compounds from C. grandiflora leaves and development of the botanical herbicides.