Ligusticum tenuissimum belongs to Umbelliferae, and its root is generally used in headache, common cold and arthralgia L. We have extracted and isolated butylidene phthal ide, 3-butylidene-4,5-dihydrophthalide of phthalide group and l-limonene, etc. of terpenoid group from the root by ordinary method. In Ligusticum sinense, L. jeholense, L. tenuissimum, L. jeholense var. tenuisectum, and L. officinale etc., the components of cnidilide, ligustilide of phthalide group are common features and specific constituents in genus Ligusticum. Therefore comparing that there is no phthalide group in genus Angelica, we think it is able to classify the difference of genus between Ligusticum and Angelica of Umbelliferae in chemotaxonomy.