Objective To study the single and combined-enzymic hydrolysis conditions of Oreochromis niloticus skin collagen.Methods Based on the inhibitory activities of six kinds of single enzymic hydrolysates to angiotensin converting enzyme(ACE),bromelain and alcalase(2.4L) were selected as combined-enzyme.The optimal hydrolytic conditions of the skin collagen with the two enzymes were determined by orthogonal test L_(16)(4~(5)).Results and Conclusion The results showed that the optimal hydrolytic conditions of bromelain and alcalase 2.4L were temperature 45℃,pH4.5,E/S 4000U?g~(-1),time 4h,concentration of substrate 6%;and temperature 55℃,pH7.5,E/S 6000U?g~(-1),time 2h,concentration of substrate 4%,respectively.Furthermore,hydrolytic effect would be better when using bromelain in advance,followed by alcalase 2.4L.The hydrolytic degree of the hydrolysates prepared under the provided technology was 30.43%,the ACE inhibitory rate would be as high as(68.65%) in vitro.