Surface acoustic wave (SAW) gas sensor is often used to monitor toxic or hazardous gases,for it exhibits high sensibility,convenience,fast response and other advantages. The spin coating technique of the polymer film on the surface of SAW sensing device has become a hot spot.In this method, the Silicon based fluoroalcohol polymer is dissolved in acetone and coated on the surface of SAW device using spin coating method.By a network analyzer, the quality factor (Q) and insertion losses (dB) are measured to determine the influence of different areas of SAW gas sensors and different viscosity of polymer to prepare SAW gas sensors.It is concluded that the ring center area on surface acoustic wave substrate is the best film area and specific viscosity less than 0.34 should be accepted.