The invention belongs to the technical field of 
genetic engineering and particularly relates to dsRNA of a 
migratory locust fatty acid elongase gene LmElo and a preparation method and application of the dsRNA. The preparation method of the dsRNA of the 
migratory locust fatty acid elongase gene LmElo comprises the following steps of a, designing an upstream primer sequence and a downstream primer sequence and synthesizing the upstream primer sequence and the downstream primer sequence; b, combining with upstream and downstream primers for designing the 
migratory locust fatty acid elongase geneLmElo, obtaining a full-length fragment of the fatty acid elongase 
gene through PCR amplification, purifying an obtained product, 
cloning and converting the product into 
escherichia coli, performing sequencing, conducting 
verification and obtaining the full-length 
nucleotide sequence of the gene, wherein the 
nucleotide sequence is shown as SEQ ID NO:1; c, designing upstream and downstream primersof the dsRNA on the basis of the sequence of the migratory 
locust fatty acid elongase gene which is shown as SEQ ID NO:1, wherein the sequences of the upstream and downstream primers are shown as SEQID NO:3 and SEQ ID NO:4 respectively, and the upstream primer and the downstream primer both carry a T7 
promoter subsequence; d, carrying out transcriptive synthesis of the dsRNA.