In the paper a new sensor structure for surface acoustic wave gas system is presented. A bilayer structure WO_3-Pd thin films may be useful for hydrogen detection in low concentration in air. A bilayer sensor structure of tungsten oxide WO_3 with a very thin catalytic film of palladium on the top has been studied for gas-sensing application at room temperature (about 25°C) in surface acoustic wave system. The bilayer structure of WO_3 layers with a thickness of about 50 nm, 100 nm and 150 nm was made onto a LiNbO_3 Y-cut Z-propagating substrate by means of the vacuum sublimation method using a special aluminum mask. The vapor source consisted of commercially available WO_3 powder (Fluka 99.9%) and molybdenum heater. The thin palladium (Pd) layer (about 10 nm) was made separately on each WO_3 layer by means of vapor deposition in high vacuum. There have been investigated three structures: 50 nm WO_3 + 10 nm Pd, 100 nm WO_3 + 10 nm Pd and 150 nm WO_3 + 10 nm Pd in three canal surface acoustic wave system with reference oscillator. Numerical results obtained by analysis of the surface acoustic wave gas sensor model have been compared with experimental results.