Abstract: Menthol extract (93.5%) was selected as the research object, and the purity of menthol crystals that formed in three kinds of solvents (acetic acid-water, ethanol-water and acetonitrile) in the electromagnetic field was detected by gas chromatography-mass spectrometer.The results showed that crystallization velocity of menthol crystals was significantly improved and the purity is increased in the electromagnetic field with intensity of 0.5T.The purity of menthol crystals is up to 99.1% in the solvent of acetonitrile in the electromagnetic field.