Abstract: The affection of different factors on the hydrolytic degree of silk fibroin peptide and the inhibiting ability formation of block pigmend of silkworm blood were studied while the silkworm cocoon was treated by gegumming, salt dissolution and alkali hydrolysis.The result showed that temperature had the most greatly influence to the hydrolytic degree of silk fibroin peptide, second factor was time, the concentration had the least influence. The inhibition ratio was only 28 34% when the silk protein was unhydrolytic, but it could rapidly reach to 48 95% when the silk fibroin was hydrolyzed. The highest value of the inhibition ability ratio for the formation of the black pigment was 67 14% while the hydrolytic degree of silk fibroin peptide was 0 476 5 g/L. Then, the inhibition ratio of the formation of the black pigment was reduced with the increase of the hydrolytic degree of silk fibroin peptide.