For the production of Casein Phosphopeptide(CPP) inhibiting the insolubility of calcium, 10% sodium caseinate was treated with 1.5% of protease from Streptococcus sp.. Optimal conditions and productivity for the CPP production, and properties of the CPP were compared with tryptic hydrolysates of sodium caseinate. Optimum conditions of pH, temperature and reaction time were 8.0, 50C, 4 hrs, respectively. Under these conditions the productivity of CPP was 23% and Molecular weight of CPP was ranged from 3, 000 to 17, 000. The results also showed that the insolubility of calcium was completely inhibited by using 1.5 times of CPP for the amount of calcium.