Degreased silkworm pupae protein was the byproducts of filature,we have found that the hydrolysates of silkworm protein hydrolyzed by acid protease (Asperqiius usamii NO 537) with Angiotensin I-Converting Enzyme inhibitory activity,but there were many protein components in it,what are the hydrolyzing characteristics of these protein,and how about the relationships between the hydrolyzing characteristics and Angiotensin I-Converting Enzyme inhibitory activity were the purposes of this paper.