NiO-In2O3 composite nanofibers are synthesized via electrospinning and calcining techniques. Micro-sensors are fabricated by sputtering Pt electrodes on Si chips to form sensor substrates, and then spinning the NiO-In2O3 composite nanofibers onto the sensor substrate surface. The as-fabricated micro-sensors exhibit excellent H2S sensing properties at room temperature. The sensitivity of the micro-sensors is up to 6 when the sensors are exposed to 3 mu L/L H2S, and the corresponding response and recovery times are 14 and 22 s, respectively. The micro-sensors also exhibit high selectivity and good stability. Especially, the micro-sensors can operate at various humidity conditions. The sensitivity of the micro-sensors is 3.8 to 3 mu L/L H2S at 75% relative humidity. These characteristics make the micro-sensors good candidates for practical H2S sensors with high performance.