High quality ZnS: Eu2 + gas- sensitive materials have been synthesized by the ultrasound assisted hydrothermal/solvothermal method, and a gas sensor which contains ZnS: Eu2 + gas- sensitive film, simple chamber, miniature fiber optic spectrometer as well as the supporting software has been put forward. The gas sensor has good stability and strong anti-jamming capability. It is found that the H2S gas concentration and the sensitive component′ s fluorescence quenching signal correspond to linear relationship via fluorescence quenching Stern- Volmer equation, which indicates that the gas sensor responds quickly and can be used for high sensitivity real-time online monitoring of H2S gas concentration.