To obtain more information about the genetic relationship between domestic and wild silkworms, we collected domestic silkworms (Bombyx mori L.) and wild silkworms (B. mandarina Moore) from China and Japan, respectively. Total mRNAs of domestic and wild silkworms were extracted, and COⅠ and NADH-6 genes from mtDNA were cloned by RT-PCR and analysed by DIG-RFLP method. The results showed that the Chinese domestic silkworm had the same molecular diversity as that of the Japanese domestic silkworm and Chinese wild silkworm, but had different diversity from that of the Japanese wild silkworm. The results suggested that both Chinese and Japanese domestic silkworms originated from Chinese wild silkworm but not from Japanese wild silkworm.