We investigate surface acoustic wave (SAW) sensor for chemical and biological detector as measuring the frequency shift based on adsorption quantities of chemical analyte on SAW propagation path. Important features that define the performance of these sensors are selectivity, sensitivity, stability, response time and dynamic range. In this paper, two inter-digital transducers (IDT) for working frequency of 50MHz, 100 MHz were designed and fabricated using conventional lift-off technique. The shift in SAW velocity due to surface loading leads to a shift in phase, which in turn generates a shift in frequency of the oscillator is confirmed. By different concentration of chemical vapor, the sensitivity of SAW devices will be presented.