Abstract: The sap_sucking insects belong to the order Homoptera , which include some of the most devasting insect pests worldwide. Plant lectins have been shown to be insecticidal to pests including Homopteran pests.In this paper we give a detailed review about the transition of the definition, the physiological role in plant body, and the mode of action of lectins. Furthmore, we describe the crop serious damage caused by Homopteran pests,and studies on transgenic plants xpressing lectins which confer protection against such insect pests. The problem in lectins genetic engineering and its future are also discussed.