Abstract: Golden pompano viscera was taken as raw material in the present study.Acid protease was obtained by homogenation of tissue in sodium phosphate buffer( p H7.0),precipitation by 0~55% ammonium sulfate,Sephadex G-100 gel and Sephadex G-50 gel.Then the enzymatic characterization was also studied. The experimental results showed that the molecular weight of purification enzyme was 18.5 ku,the optimum p H was 4.0 and the most suitable temperature was 35 ℃. It had good acid stability and salt tolerance. Using hemoglobin as a substrate,the Kmwas 10.13 g / L. Pepstatin A inhibited the enzyme,while EDTA,E-64 and PMSF had no influence on the enzyme,which indicated that this enzyme was probably aspartic proteinase.It had the similar hydrolysis ability of gelatin of tilapia fish skin to papain and alkaline protease,and stronger than porcine pepsin.