An improvement in the apparatus, which is able to determinate 10^-6 mole of essential oil in a few milligrams of a sample, has been established. The apparatus is suitable for the analysis of essential oils, especially of the essential oils solid at room temperature and heavy density essential oils, using a small portion (0.1-1 g) of crude drugs and plant tissues. The method is applied for the analysis of drugs containing essential oils, perfume, flavour, and cosmetics, and essential oils in the decoction of Chinese medicines.