Abstract: In order to realize the development and utilization of sheep placenta, the optimal combination scheme for the composite enzymatic hydrolysis of multiple proteases was investigated with the indicators of the yield of peptide ( PY) and the degree of hydrolysis ( DH) .On this basis, the ultrasonic pretreatment parameters of sheep placenta were optimized by response surface methodology ( RSM) .The results showed that the optimal conditions of ultrasound pretreatment were found as follows:ultrasonic time of 18 min, temperature of 28 ℃ and power of 420 W. Under these optimal ultrasound pretreatment conditions, synchronous composite enzymatic preparation by papain and flavor enzyme of the PY was 39.89%, the DH was 21.78%.And the average chain length was 4.59 and the molecular weight was about 500 ~ 600. Conclusion: the ultrasonic assisted enzymatic preparation method was feasible and effective in the preparation of Tibetan sheep placenta peptide.