Display omitted •Pd decorated WO3 exhibited ultrafast detection of H2S.•Response to H2S of WO3 sensor increased by 250 times after Pd-decoration.•Mechanism for enhanced sensing performance of Pd decorated WO3 was proposed. Sensors based on pristine and Pd/PdO-loaded WO3 microspheres (NWs) were fabricated for H2S detection. Solvothermal method was employed to synthesize pristine WO3 microspheres. The Pd/PdO decoration procedure was realized by immersing the pristine WO3 into the solution with Pd precursor. Pd/PdO nanoparticles with diameter around 4−7 nm were successfully loaded on the surface of the WO3 microspheres characterized by SEM, TEM, HRTEM, EDS and XPS. Sensing performances were systematically investigated with varying Pd loading amount (0 at%, 1 at%, 2 at%, 5 at%). The sensitively and selectively were significantly improved after loaded with Pd. The 2 at % loaded sensing material exhibited the highest response of 1029 to 25 ppm H2S, which was 270 times higher than the pristine WO3 at 190 °C. Importantly, the sensor showed quite short response time (less than or equal to1 s) after loaded with Pd/PdO. The tremendous gas sensing enhancement could be attributed to the adjustment of the oxygen state, modulation of sensor resistance and catalytic effects of Pd/PdO. This study demonstrated that decorating WO3 with Pd/PdO is an effective route to realize the H2S detection with high response. The fabricated H2S sensor offered potential applications in the fields of rapid detection toward H2S.