In this paper we discussed, nitrogen oxides gas sensors are designed and simulated using the MEMS-based tool of COMSOL Multiphysics software. Pd-rGO composite films were designed and their NOx sensing characteristics were investigated in this study by comparing with/without active layers. Transition metal SnO2 deals with four different active materials i.e., Pure SnO2, SnO2-Pd, SnO2-rGO, and SnO2-Pd/rGO film was controlled by altering the active materials during the active layer deposition. The deposition of Pd/rGO active material is integrated into the SnO2 thin film. The response of the nanocomposite materials on the NOx gas sensor at a low temperature below 100 °C was significantly improved. Moreover, we investigate the optimization from different active layer response for NOx by applying power in watt and milliwatt to the interdigitated electrode on the Sn substrate. The determination is tense to finalize the suitable materials that to detect more response for nitrogen oxides i.e., Pd/rGO layer shows better performance when compared with other active layers for the sensing of nitrogen oxides is in proportion to the power in the range of 0.6-4.8 W at (1-8) Voltage range. This advanced research will enable a new class of portable NOx gas sensors to be constructed with millimeter size and microwatt power.