Abstract: The present invention provides methods for the preparation of protein hydrolysate, peptide solution and peptide from BSG. The wet BSG or BSG powder is dispersed in extract solution to prepare the crude BSG protein or the crude BSG protein solution. Preparing the crude BSG protein solution using the crude BSG protein and adjusting the pH to 6.5˜8.5, or adjusting the pH of the crude BSG protein solution to 6.5˜8.5. Then the solution is hydrolyzed with protease at 45° C. to 65° C. for 1 h to 5 h in a water bath shaker to prepare BSG protein hydrolysate. The protein hydrolysate is heated to inactivate the protease and centrifuged to obtain the peptide solution. The peptide solution is separated by gel filtration and each peak is collected and pooled together to obtain the peptide. The protein hydrolysate, peptide solution and peptide in the present invention are all prepared from BSG which is a natural product and available at low cost throughout the year.