Determination of H

2

S in SF

6

decomposition products plays an important role in assessment of the insulation state in SF

6

insulated electrical equipment. H

2

S can be detected by ultraviolet absorption spectrometry for its absorption in the band of 190

2

30 nm. We set up an ultraviolet detection platform for the determination of H

2

S. However

the sensitivity of H

2

S detection was low because the absorption spectra were easy to be interfered by spectral scatting and high-frequency noise. Therefore

ultraviolet difference algorithm and wavelet function were used for volu

me fraction inversion to obtain the relationship between spectral data and gas volume fraction. The research results show that there is a good linear relationship between the frequency domain information obtained by spectral data extraction and the concentration

the method shows good linearity（R2=0.999 9） and the volume fraction limit of the detection is 0.590×10

-6

. The obtained inversion expression was used for the actual data detection

and a good detection effect was obtained. The method is of good detection repeatability and high sensitivity

and it can be integrated into portable testing equipment

which is suitable for on-line detection of trace H

2

S in SF

6

insulated electrical equipment.