Preparative high-speed countercurrent chromatography has been usedsuccessfully for the isolation and purification of imperatorin，oxypeucedanin andisoimperatorin from traditional Chinese herb "bai zhi" -Angelica dahurica(Fisch. ExHoffm)Benth. Et Hook by using high-speed countercurrent chromatography(HSCCC).This was achieved in two stages. The first stage used a high flow HSCCC protocol with atwo-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water(HEMW)with volume ratios of 5:5:5:5，v/v which isolated isoimperatorin but co-eluted imperatorin& oxypeucedanin. The second stage used HEMW 5:5:4:6，v/v at low flow rate to resolvethe co-eluted components from the first stage. The flow rate was optimized usingpreparative HSCCC. 300 mg amount of the crude extract was separated，yielding 18.5 mgof imperatorin，8.3 mg of oxypeucedanin and 9.8 mg of isoimperatorin all at a high purityof over 98％.