Previous studies have revealed that a point mutation of a target gene is related to insecticide resistance to pyrethroids.The para sodium channel in the insect central nervous system is the target of pyrethroid insecticides.We used the RT-PCR method to clone the para sodium ion channel in the silkworm, Bombyx mori L.（GenBank No.EF521818）.The full length of this cDNA fragment is 4 882 base pairs and its partial ORF is 3 986 bp translated into 1 328 amino acids.BLAST analysis demonstrated that the cloned cDNA fragment is virtually identical to the para sodium channel α subunit gene amplified from other insects.Amino acid homology of the cloned fragment with para sodium channel α subunit genes from Heliothis virescens Fabricius, Aedes aegypti L., Blattella germanica L., Drosophila melanogaster Meigen and Musca domestica L.was 95%, 82%, 80%, 79% and 77% respectively.