Abstract: The properties of Alcalase hydrolyzing silk fibroin were studied.The results showed that the optimum conditions for Alcalase were 50 mg/mL substrate mass concentration,pH 9.0 and 60 ℃.The main amino acids of silk fibroin peptide were glycine,alanine,serine and tyrosine with a total amount of approximately 85%.The relative molecular weights of the main components of silk fibroin hydrolysate with DH 17% were 249 Da and 762 Da respectively,the contents about 72.9% and 15.5% respectively.The relative molecular weights of the main components of silk fibroin hydrolysate with DH 21% were 209 Da and 668 Da respectively,the contents about 84.4% and 7.2% respectively.