The catalytic performance of ruthenium (Ru) in the synthesis and decomposition of ammonia (NH 3 ) has attracted extensive attention and research. Considering its selective adsorption and excellent catalytic effect toward NH 3 , it holds significant potential in the field of ammonia detection. In this study, we present a high-performance NH 3 sensor that was based on a catalytic metal gate field-effect transistor (FET) utilizing Ru nanoparticles as the sensitive gate (Ru-FET). The sensor exhibits a high response of 11.3% to 1 ppm of NH 3 at room temperature, with quick response and recovery processes of 8 and 85 s, respectively. Meanwhile, the sensor possesses a detection range of 0.4−20 ppm along with good repeatability and selectivity. The exceptional performance of the Ru-FET sensor suggests the potential of judiciously combining sensitive materials and sensor structures to manufacture high-performance NH 3 sensors operating at room temperature.