Abstract: The use of allelopathy and allelochemicals of pla nts to agriculture production depends on the understanding of allelopathy of pla nts.The results of previous studies showed that,as a message molecule,allelochem ical acts on target sites of plant cells,and then the target sites in turn conve y the message to inner cells,thus influencing membrane permeability,cell differ entiation,phytohormone generation,ions uptake, protein synthesis and gene statem ent,and so on,and eventually inhibiting plant growth.But action modes and sites of allelochemicals need to be further studied.