Abstract: Low-temperature continuous phase transition was applied to extract fish oil from Decapterus Maruadsi.The effects of moisture content,extraction temperature,pressure,extraction time,separation temperature on the yield of fish oil were investigated,the optimum extraction conditions were determined by response surface experiment,and the physicochemical properties and fatty acid compositions of fish oil were also analyzed. The results showed that the optimum extraction process of fish oil extracted by low-temperature continuous phase transition was obtained as follows: the moisture content of 11%,extraction temperature of 52 ℃,extraction time of 62 min,extraction pressure of 0.6 MPa and separation temperature of 65 ℃,and the optimum conditions of fish oil yield was 21.56%.The fish oil was yellow to brown and lighter fish smell,physicochemical indicators had reached the first standard of SC / T3502- 2000 for crude fish oil. Eighteen kinds of fatty acids were identified by gas chromatography-mass spectrometry( GC- MS),and the total yield of unsaturated fatty acids was as high as59.57%,the total yield of EPA and DHA was 24.62%. Low-temperature continuous phase transition technology applied in oil production,had the characteristics of high efficiency,low extraction temperature,less damage to the components of the oil and so on,and showed good economic benefit and application prospect.