Production method of biological polypeptide used for feed

This invention relates to a production method of a biological polypeptide used for feed, and the biological polypeptide can substitute for plasma protein in the feed. The biological polypeptide consists of: soybean polypeptides, a hydrolyzed yeast complex and a composite micro-ecological agent. The production method comprises the following steps: carrying out fermentation and enzymolysis on the soybean polypeptides, preparing the hydrolyzed yeast complex and preparing a product. The product obtained in the invention can completely substitute for the plasma protein in the suckling pig feed, provide high-quality protein ingredients for the feed, simultaneously improve piglet immunity, reduce piglet diarrhea, promote piglet growth, lower feed conversion and increase breeding benefits.