In this paper the experiments were carried out to study the allelopathy of Ophiopogon japonicus extracts on Lactuca sativa,Cucumis sativus and Raphanus sativus.The results showed that the water extracts of underground and aboveground parts of Ophiopogon japonicus had significant inhibiting effects on the seed germination rate of Cucumis sativus and Raphanus sativus,but no obvious inhibiting effects on that of Lactuca sativa.The extracts also had inhibiting effects on the growth of the main roots of the tested plants,while accelerating the stem growth of Cucumis sativus.