A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation of four major sesquiterpenoids with similar structures, namely ar-turmerone, -turmerone, -turmerone, and E--atlantone, from the essential oil of Curcuma longa Linn. using a two-phase solvent system composed of n-heptane-ethyl acetate-acetonitrile-water (9.5/0.5/9/1, v/v). From a single HSCCC run, 1.7861 g of ar-turmerone, 0.4708 g of -turmerone, 1.3427 g of -turmerone, and 0.1650 g of E--atlantone were obtained. The purity of each compound was over 98% as determined by HPLC. The chemical structures of these compounds were determined by H-1 NMR and C-13 NMR.