The extraction process of mixed fatty acid from soybean oil sediment was researched. Soybean oil sediment was hydrolyzed by hydrochloric acid. The mixed fatty acid was extracted by Soxhlet extractor or vacuum rotary evaporator. The optimal technical condition was obtained by orthogonal experiment, which was: with Soxhlet extractor, heating time was 45 min, temperature 75 ℃, the concentration of hydrochloric acid 22%; with vacuum rotary evaporator, heating time was 45 min, temperature 75 ℃, vacuum degree 91.9 kPa. The result showed that the fat acid content 98.8% extracted with vacuum rotary evaporator was higher than that with Soxhlet extractor, which was 90.18%. The vacuum degree and the concentration of hydrochloric acid had a certain influence on the extraction of fat acid content, while heating time and temperature had little influence.