The innovative application of microwave transduction technology in the field of gas sensors make it possible to develop wireless passive room-temperature gas sensor integrated on wearable device. Herein, the ultranarrowband microwave filter was designed as microwave transducer device, and the microwave sensing measurements were extended to reflected coefficient. Meanwhile, the SnO₂/bionic porous (BP) carbon composites based thick film were deposited on the coupled line spacing blank surface via blade coating method. According to the SnO₂nanoparticles were well distributed on BP carbon with abundant micro pores, the gas adsorption and desorption can be enhanced, and the sensor response signal base on microwave transduction was finally improved. Without the influence of temperature and humility, the proposed SnO₂/BP carbon microwave gas sensor exhibited excellent NH₃sensing behavior at room temperature including wide concentration range (10–200 ppm), relatively fast response and recovery rate, superior selectivity, as well as good reversibility and stability. More importantly, the dielectric constant of microwave sensor has been proved strongly correlation with injected ammonia concentration. This work further proves the feasibility and frontier of microwave transduction technology in gas sensor application