Effective components, ligustilide and butylidenephthalide, from Ligusticum Chuanxiong (Ligusticum wallichii Franchat, Umbelliferae) werescreened and identified by using a cell membrane chromatography (CMC) and a gas chromatography/mass spectrometry (GC/MS). Thecomponents showed the effects of inhibiting vasoconstriction in vitro on rat abdominal aorta segments. The screening procedure was performed ina rat artery CMC column (50mm×2.0mm I.D.) with a sodium phosphate buffer (pH 7.4) as mobile phase at 37℃. The identification wasaccomplished by a DB-5MS 30m capillary column (0.25 mm I.D., 0.25 Am film thickness) with helium as carrier gas operating under programcontrol temperature and electron impact ionization mass spectrometer in a scan mode. Results demonstrated that ligustilide andbutylidenephthalide can act on rat artery cell membrane similar to verapamil in CMC system. They significantly inhibited the vasoconstrictionsinduced by norepinephrine bitartrate (NE) and calcium chloride (CaCl2). The relaxing effect of ligustilide on the NE-and CaCl2-inducedconstrictions is more potent than that of butylidenephthalide. Ligustilide and butylidenephthalide seem to be the two main effective components ofLigusticum Chuanxiong as a traditional Chinese medicine for treating blood vessel diseases.