Abstract: Provided is a method for Bombyx mori silk fibroin heavy chain mutation including causing the mRNA of a coded zinc-finger nucleases sequence to act upon a target point such as positions 1325-1362 of Bombyx mori silk fibroin heavy chain gene as expressed in SEQ ID NO:1 so as to obtain a series of Bombyx mori silk fibroin heavy chain mutated genes. Also provided is a mutation sequence prepared according to the method. Also provided is the use of the mutation sequence in the preparation of sericin and foreign proteins. Also provided is a Bombyx mori mutant including the described mutation sequence as a novel Bombyx mori salivary glands bioreactor, the posterior salivary glands of the mutants being severely degraded and the cocoon layer thereof including sericin synthesized and excreted by the middle salivary glands.