Abstract: Plant allelopathy is a favorable or harmful effect produced by one plant on another through production of chemical compounds that escape into the environment．In recent years，much progress has been made on distillation，purification，identification，and bioassay of allelochemicals．Allelochemicals are mainly secondary substances of plant，which can influence plants growth by affecting membrane system ，hormone level，minerals uptake，photosynthesis，and respiration．In this article，plant allelopathy is summarized，and research methods and mechanisms of allelopathy are mainly introduced，problems and trends in plant allelopathy research are discused too．