In this letter, a microwave gas sensor (MGS) is proposed for detecting H₂S, based on a differential complementary split ring resonator (DCSRR) with Pd-doped CdSnO₃ (Pd-CdSnO₃) loaded in the region confining a strong electric field (E-filed). Pd-CdSnO₃ converts changes of H₂S concentration into variations in electrical properties, synergizing with the strong E-filed of DCSRR and reflected in the alterations of the reflection coefficient. Benefiting from the spill-over effect and superior catalytic activity of the employed Pd for H₂S, as well as the synergism of Pd-CdSnO₃ and DCSRR, the proposed MGS exhibits excellent sensing performance. At room temperature, the proposed MGS achieves a high sensitivity of 0.49 dB/ppm for low (1 ppb-0.2 ppm) and 0.21 dB/ppm for high (0.5-50 ppm) concentrations of H₂S. In addition, the proposed MGS exhibits a low experimental detection limit of 1 ppb and high selectivity.