Analyzing the dynamic change of composition and concentration of SF₆ discharge decomposition products is the key to SF₆ Gas-Insulated Switchgear （GIS） state diagnosis. This paper proposed a dynamic and high-sensitive detection method based on fluorescence-suppressed Fiber-Enhanced Raman Spectroscopy （FERS）. Firstly， a fluorescence-suppressed FERS gas detection system of SF₆ discharge decomposition products is established. With a Synergistic Fluorescence Filtering method combining CCD digital noise filtering and iris noise reduction， the signal-to-noise ratio of the system is increased by 228.4%. Based on Allan variance analysis， the optimal integration time of the system is determined to be 220 s. Next， by analyzing standard mixed gas samples under 2 bar pressure and 220 s integration time， the characteristic Raman peaks for qualitative and quantitative analysis of SF₆ discharge decomposition products SOF₂， SO₂F₂， COS， CF₄， SO₂， CO₂ and CO are determined， and the lower limits of detection are calculated to be 1.95， 1.78， 0.83， 2.41， 0.93， 2.51， 6.69 ppm， respectively. Finally， by a 168-hour continuous partial discharge experiment in a reduced scale GIS model， the fluorescence-suppressed FERS gas detection system is proved capable of dynamic and high-sensitive detection of SF₆ discharge decomposition products， and the deviation from gas chromatography result is within ±5%. Experimental results demonstrate that the proposed detection method can provide technical support for the safe operation of GIS.