Abstract: RNAi has become one of the hotspots of scientific research in 21st century.It has been widely used to investigate gene functions,the abilility of diseases resistance and the regulation and control of growth and development.In this paper,the mechanism and significance of RNAi and its application in plant were summarized with 33 references.The problems of RNAi were discussed,and the future of RNAi in plant was prospected.