Polycristalline Pt-doped SnO2 thin films have been integrated to silicon substrate by ultrasonic spray deposition. This deposition technique differs from the usual SnO2 deposition methods by using a liquid source. It allows one to obtain a very fine and homogeneous dispersion of Pt aggregates which act as a catalyst for the low temperature CO detection (25-100 degrees C) by conductance change. The influence of synthesis temperature (460-560 degrees C), concentration of Pt additive (0.1-5 at.%) on gas sensitivity has been studied. The realisation of gas sensor includes a gas sensitive highly porous layer (SnO2/Pt, thickness: similar to 1 mu m). The results of electrical measurements under 300 ppm of CO for thin films in a dynamic and quasistatic regime are discussed. The narrow peak of gas sensitivity in the range of low temperatures (25-100 degrees C) is obtained for about 2 at.% Pt in the SnO2 film.