Bacillus thuringiensis (Bt) is a gram-positive bacterium that produces parasporal crystal proteins known as endotoxins or Cry proteins. The Cry protoxins are then cleaved by insect midgut proteinases to form active Bt toxins. The activated Cry protein then binds to specific receptors at the midgut epithelium. Cadherin-like and aminopeptidase N (APN) proteins are involved in Bt toxin binding by interacting sequentially with different toxin structures. Aminopeptidase N (APNs) from several insect species have been shown to be putative receptors for these toxins. We have characterized four different midgut APNs(APN1, APN2, APN3, APN4) cDNAs from S. exigua. Forward primers and reverse primers for confirmation of four different midgut APNs were designed based on their sequences cloned from the cDNA libraries. Quantitative RT-PCR procedures includes 42℃ for 20min (cDNA synthesis), 99℃ for 5min, and 35 cycles (94℃ for 1min, and 60℃ for 50 s) for collection. Four aminopeptidase N isoforms were confirmed with qRT-PCR. Sequence analysis was performed by BlastX search the National Center for Biotechnology Information(NCBI) nucleotide. Furthermore, double-stranded RNAs(dsRNAs) were synthesized. DsRNAs were determined for bioassay.