Papain was applied to the Paphia undulta protein for hydrolyzation in this study. The hydrolysis conditions that could produce the highest hydrolysis degree were determined. Furthermore, the optimal enzymatic hydrolysis condition that could produce the protein hydrolysates was also determined by the orthogonal design. The results were temperature 40 ℃, time duration 4 h, enzyme content 6000 U/g, substance concentration 1∶10 and pH6.5. The contents of free amino acid in hydrolysates amounted to 492.32 mg/100 mL, among which the percentage of essential amino acid was 30.6% . The experiment results showed that hydrolysate by papain was used to develop health foods and natural flavoring agent.