A method for improving plant insect resistance includes providing target genes derived from insects. Constructs based on the nucleotide sequences of these target genes are designed to form interfering molecules. After being eating by insects, the plant can significantly inhibit expression of corresponding genes in insects. This inhibition is not affected by barrier of the insect digestive systems. The method can improve the insect resistance of plants, reduce pesticide applications, lower the costs of agricultural production, and protect the environment.