The　C12-sensitive　heteropolysiloxanes(HPS)　film　was　formed　on　the　interdigital　capacitor　based　on　silicon　dioxide　by　means　of　sol-gel　process　and　spin-on　technique.　Measurements　of　interdigital　capacitance　were　performed　at　room　temperature　for　frequencies　100　Hz,　1　kHz　and　10　kHz.　It　is　shown　that　there　is　a　linear　relationship　between　the　capacitance　and　the　concentration　of　chlorine　gas.　Influences　of　the　measurement　frequency　and　film　thickness　of　silicate　on　the　sensitivity　of　the　sensor　to　C12　gas　were　discussed.　And　organically　modified　N,N-diethylaminopropyl-trimethoxysilane　(APMS)　had　a　much　higher　sensitivity.