Abstract: By means of CVD method, the thin film of tin diohloride doped with a single foreign ion is deposited on the purified ceramic substrate. The raw material of the element is anhydrous tin tetrachloride doped with single foreign ion. The range of working temperature of the element is 250 to 360℃. In this range of temperature, the element can detect the existence of alcohol vapor of concentration 2r/ml in the air. The element is non-ohmic contact element. Its response time is about six minutes and its life time longer than 1,000 hours.