Abstract: In this study,the complex of trypsin and flavor protease was used to deeply hydrolyze grass offal. Response surface methodology(RSM)was applied to optimize the enzymatic hydrolysis process of grass offal protein and maximize the content of free amino acids in its hydrolysates by assessing the factors of enzymatic hydrolysis temperature,pH,liquid material ratio and enzyme addition,using total free amino acids as response factor. The result showed that the complex of trypsin and flavor protease had an effective hydrolysis on grass carp. The maximum ∑FAA of its hydrolysates could be obtained when composite ratio was 3:1. In addition, temperature, pH,solid-liquid ratio and enzyme dosage had a significant(p<0.05)effect on its hydrolysis degree. The maximum ∑FAA of its hydrolysates was(12.03±0.11) mg/mL when temperature was 50℃,pH was 7.3,liquids to material ratio was 4.2:1,enzyme dosage was 2.2% and time was 6 h. 17 kinds of free amino acids were detected in the enzymatic hydrolysate. The content of different amino acids increased significantly as the time of enzymatic hydrolysis was extended. When the time of hydrolysis was over 6 h,increased trend of free amino acids obviously slow down. Hence,the established preparation technology could be used to produce protein hydrolysates of grass offal.