A kind of mixed-potential-type gas sensor based on yttria stabilized zirconia (YSZ) and Nickel series spinel structure oxides electrode was designed for detection of low concentration hydrogen sulfide (H₂S). Among three oxides (NiMn₂O₄, NiCr₂O₄and NiFe₂O₄) prepared by solvent evaporation method, hollow balls NiMn₂O₄exhibited the highest sensitivity to H₂S gas in air at 500℃. Results of scanning electron microscope (SEM) and X-ray diffraction (XRD) revealed that micro-structure of materials could be influenced by the rate of reagent dropping in the solvent evaporating process and sintering temperature. Then, the relationship between sensing performance and micro-structure of NiMn₂O₄was investigated. As a result, the sensor using NiMn₂O₄with hollow balls (diameter 5-8 mu m) structure as the sensing electrode showed the best performance to 50 ppb to 2 ppm H₂S at 500 degrees C. The Delta V value of the sensing device exhibited segmentally linear relationship to the logarithm of H₂S concentration and the slope was -35 mV/decade (50 ppb to 200 ppb) and -125 mV/decade (500 ppb to 2 ppm), respectively. The sensing device also showed an excellent selectivity. Finally, electrochemistry polarization curve measure was taken to further prove the mixed potential sensing mechanism.