To determine the best extraction solvent of walnut roots,the allelopathic activities of root extracts from walnut were tested against wheat,cabbage and mung bean by the indicator of synthesis effect (SE) on seed germination and seedling growth.The allelopathy of different extraction phases from 95% ethanol extracts was also studied.The result showed that:95% ethanol extracts of walnut roots had the strongest inhibition on the seed germination and seedling growth of three acceptors (SE=－0.559).When the tested mass concentration was 40 mg/mL,the inhibited effect of different extracts from 95% ethanol extracts on root length of three acceptors was greater than it on seedling height,with the most significant integrated allelopathy of ethyl acetate extracts (SE=－0.571).The inhibition rate of root length and seedling height of wheat and cabbage was above 60%; cabbage is more sensitive than wheat and mung bean.Different mass concentration treatments of ethyl acetate extracts had different allelopathy intensity to three acceptors.As the increasing of mass concentration,root length,seedling height and relative water content of wheat were inhibited,significantly lower than control.The allelopathic effect on cabbage and mung bean presented dual effect; low mass concentration promotes growth,while high mass concentration inhibits growth.