Abstract: The allelopathic effects of walnut(Juglans regia L.) leaf extracts on three plant acceptors:lettuce, wheat and tomato was explored by germination and growth experiments.Results showed that different concentrations of aquatic walnut leaf extracts had certain inhibitory and/or promoted effects on those acceptors, and major bioactive substances were found to be phenolics and flavonoids.This study can provide some basis for development of biorational pesticides.