The invention discloses a silk 
protein peptide fragment for identifying a novel natural color silkworm. A 
gene sequence of the silk 
protein peptide fragment comprises domestic silkworm silk H chain amorphous region genes, recombination genes of an H chain crystalline region and an H chain amorphous region, tussah H chain genes and natural silkworm silk H chain genes. The invention further discloses a preparation method of the silk 
protein peptide fragment. The preparation method comprises the following steps of 
cloning of the silkworm silk amorphous region genes of the domestic silkworm variety and the establishment and expression of an 
expression vector; 
cloning of the recombination genes of the silkworm silk crystalline region and the silkworm silk amorphous region of the domestic silkworm variety and the establishment and expression of an 
expression vector; and 
cloning of the silkworm silk genes of the natural color cocoon variety and the establishment and expression of an 
expression vector. The method is simple and easy to implement, and ensures that the sequence is accurate and errorless, and the 
gene mutation or the 
gene deletion of each established expression vector is avoided, so that the triple-coded mispairing or the exceptional 
amino acid errors of expression products cannot be generated, and thus an obtained product can be further prepared into a silkworm silk 
antibody with high precision. At the present, the report related to the preparation of the 
peptide fragment from the white domestic silkworm silk variety (silk protein amorphous regions and crystalline regions /  amorphous region units) and the yellow tussah silk variety or green natural silkworm silk variety is not provided.