Abstract: The coating material used as deactivating substance for stainless steel columns in gas chromatography has been prepared by dynamic processing of 30% propanone solution of polyphenylsilsesquioxane(PPSQ) and aged at high temperature. This coating is thermal stable under 400℃ and solvent stable. The chromatagraphic behavior of said coating was studied by GC with a pre column of a 2 mm×3 m Teflon column packed with Parapack-Q and the test column under isothermal condition. The test mixture was a solution of methanol, ethanol, iso propanol and tert butanol in water with the concentration of 0.6 ng/mL. The experiment results indicate that the active sites on the inner surface of the stainless steel columns have been shield effectively by the coating. The inertness of the treated column is nearly the same as the pre column. The IR spectra indicated that there are phenyl and hydroxyl groups in the structure of the coating material, which can be used to improve the compatibility of other stationary phases with the inner surface of the stainless steel column and to supply active sides for preparing a bonded stationary phase.