In order to investigate the effect of magnetic field on the liquid-liquid extraction, the extraction in the acetone-water-trichloroethane system was studied under magnetic field with different magnetic induction intensity.The results showed that the effect of magnetic field was positive in the extraction process, and the partition coefficient and the yield of acetone increased with the increasing magnetic induction intensity by 5.16%-8.35% and 1.85%-5.70% respectively. The effect of magnetic field on the extraction was intensified when the temperature became higher. The experimental data of the partition coefficient of acetone were correlated by the method of least square in terms of a power-law correlation.