Abstract: 1.The present paper presents a method for preparing chromatostrip by coating one side of a glass strip with a paste of neutral alumina, gypsum, and water in the propor- tion of 5:1:7. The thickness of the paste is 1 mm, and the paste is afterward dried for 2 hours at 120℃. This gives a uniform thin layer which is suitable for the separa- tion and identification of the principal chemical constituents in essential oils. 2. By using the chromatostrips, the author succeeded in identifying the principal chemical constituents in 12 essential oils, and presented a series of thin layer chromato- graphs for 30 aromatic plants used in Chinese medicine.