Abstract: Simple and efficient surface acoustic wave (SAW) two-port resonators with low insertion loss and high Q-values on ST-X quartz substrate using a corrosion-proof A1/Au-stripe electrode structure are developed for gas sensing. It was composed of two shorted grating reflectors and adjacent intedigital transducers (IDT), and an active metal film in the cavity between the IDTs for the sensitive film coating. The devices are expected to provide good protection towards metal electrode for gas sensors application in chemically reactive environments. Excellent device performance as low insertion loss, high Q-Values and single-mode are achieved by carefully selecting the metallic electrode thickness, cavity length and acoustic aperture. Prior to fabrication, the coupling of modes (COM) model was performed for device simulation to determine the optimal design parameters. The fabricated single-mode SAW resonator at operation frequency of 300 MHz range exhibits matched insertion loss of ~ 6.5 dB and loaded Q values in the 3000 range. Using the fabricated resonator as the feedback element, a dual-resonator-oscillator with excellent frequency stability (0.1 ppm) was developed and evaluated experimentally, and it is significant for performance improvement of SAW gas sensor.