Low-cost fish protein was acylated, and then the effect of the acylation degree on the enzymatic hydrolysis of the acylated fish protein, including yield of amino acids and TCA-soluble peptide, and molecular weight distribution of peptide, was studied in this paper. Results showed that acylation significantly reduced the yield of amino acids, but improved the TCA-soluble peptides in the hydrolysates of the fish protein. For the acylation of fish protein, the best pre-incubation temperature and time and the dosage of the acylating reagent SA were 60 ℃, 30 min, and 0.3 g/g Pro, respectively, under which the highest yield of TCA soluble peptide reached 38% after hydrolyzing the fish protein for 10 h.