In view of the current situation that it is difficult to prevent and control in advance the generation of trace H2S, SO2, CS2 and CF4 gases by SF6 gas insulation equipment under fault conditions, there is no effective monitoring method and detection device. This paper studies the gas detection technology based on the UV spectrum and non dispersive infrared analysis, deeply studies the spectral characteristics of low Concentration H2S, SO2, CS2 and CF4 gas with the SF6 as background gas, and simulates the spectral absorption capacity. According to the absorption spectrum line and its variation with temperature and pressure, the concentration inversion algorithm is fitted to improve the effective detection ability of the instrument. Using optical fiber sensing technology, an optical path structure suitable for on-line detection of high-voltage equipment is designed. Using the characteristics that the optical signal is free from electromagnetic interference, the transmission of optical signal by optical fiber is studied, and finally the on-line analysis of the trace H2S, SO2, CS2 and CF4 gas components in the high-voltage equipment is realized. The high-voltage switch model is constructed through three-dimensional modeling, and its fault tolerance and anti-interference ability are analyzed. The stray light and space light are analyzed by simulation software, and the effects caused by vibration and deformation are simulated. The on-line optical fiber sensing detection method of H2S, SO2, CS2 and CF4 gas in high-voltage GIS equipment is proposed. The optical noise suppression technology suitable for the field is studied, the optical path system is designed to withstand the gas pressure of high-pressure equipment, and the influence of field vibration and temperature change of high-pressure equipment on the optical path structure is solved. The on-line gas detection experiment was carried out, and the automatic calibration simulation device of the optical path system was calibrated to ensure the accuracy and stability of H2S, SO2, CS2 and CF4 gas detected by the optical path system.