Abstract: We designed a pair of sequence specific primers from the silkworm, Bombyx mori αamylase gene that have been published on Genbank (accession number: U07847). After amplification in six silkworm strains and one Chinese mandarina strain, polymorphism about the length of products has been detected. Furthermore，the genetic diversity and phylogenetic relationship of the seven strains was investigated using the Clustalx software basing on the gene sequences information.