Abstract: Kovats retention indexes of more than 200 kinds of natural and synthetic compounds of alcohol, aldehyde, acetal, ketone, ether, alkene, nitrile, carboxylic acid, ester, etc. were determined on polar liquid phase (DB-WAX) and nonpolar liquid phase (DB-1) by linear temperature-program capillary column gas chromatography. Some rules of part of the homologous series of compounds were summed up from the retention indexes, the rules of RI vs carbon, RI vs boiling point and RI on two columns, In order to keep the retention indexes practical, effects of initial temperature (T₀), program rate(r) and average linear carrier gas velocity (ū), etc. on the retention indexes were investigated. The conclusion is that the retention indexes are highly reproducible so long as the program parameters change in a certain range.Two kinds of essences, Meigui and Linglan, were identified successfully on IBM-PC/XT microcomputer by the Data Base Management System of essential oil and essence by capillary column gas chromatography and the results are satisfactory.