Taking the bighead carp viscera as raw material and cyclonexane as the extraction solvent,we studied the extraction process of bighead carp viscera oil through ultrasound-assisted extraction.The process was optimized by three factors and three levels of Box-Behnken response surface design,and the fatty acid composition and physical and chemical indicators of the crude fish oil were analyzed.The results showed that with 4∶1 liquid-to-solid ratio at 50 ℃ within 57 min and 400 W extraction power,the extraction rate of the oil reached 94.82%.The fish oil obtained was light yellow,turbid and smelled a little,with 10.15 mg KOH/g acid value,1.53 μmol/g peroxide value,135 g I2/100 g iodine value,0.34%moisture content,and 0.38% impurity. Those indexes reached the standards of super fine crude fish oil.By means of GC/MS,13 kinds of fatty acid were identified,the main unsaturated fatty acids being oleic acid (29.95%) and linoleic acid (11.79%).Moreover,certain amounts of eicosapentaenoic acid (EPA),docosapentenoic acid (DPA),docosahexenoic acid (DHA) were also found in the fish oil.