Abstract: In this work, the crude fish oil was extracted from snakehead viscera by ultrasound-assisted n-hexane extraction, and the process conditions were optimized through single factor experiments and orthogonal experiments. Then, the physicochemical indexes as well as volatile flavor components of the obtained crude fish oil were evaluated. The results showed that the optimal extraction conditions of crude fish oil from snakehead viscera were determined as follows: Ultrasound temperature of 50 ℃, ultrasound time of 50 min, ultrasound power of 300 W, liquid to material ratio of 3:1 mL/g. Under the optimal conditions, the yield of crude fish oil from snakehead viscera was 79.80%. The crude fish oil obtained by ultrasound-assisted solvent extraction had good physical and chemical properties with lower acid value and anisidine value compared to those obtained by traditional water-boiling extraction or solvent extraction. The crude fish oil was rich in unsaturated fatty acids (64.95%), including oleic acid 23.67%, linoleic acid 24.29%, and a total content of EPA and DHA of 8.84%. Besides, the volatile flavor components of crude fish oil were mainly inorganic sulfides, methyl groups, aromatic components and organic sulfides. Ultrasonic-assisted extraction of snakehead visceral fish oil possessed an excellent yield and unique volatile flavor substances, and could delay oxidation rancidity, and increase the content of unsaturated fatty acids in crude fish oil in a certain extent.