In order to detect hydrogen sulfide ( H₂S) gas more effectively,a double-plating silver fiber Bragg grating (FBG) gas sensor is pro posed.On the one hand,the double-plating silver is adopted to increase the uni formity of the silver film and improve the sensitivity of gas sensor.On the other hand,the sensor which is designed to ach ieve the separation of oil and gas is used to ensure the effective contact between the H₂S gas and the gas sensor,an d to complete real-time detection of low concentration gas in underground mine.According to the experiment of double -plating silver FBG gas sensor, the relationship between the H₂S gas concentration and absorption spectrum is obtained.Results indicate that the energy of evanescent wave decreases and the peak power of back reflection spectrum drops b y 2.0dBm.