Abstract: The desulphurization system was established with EDTA-Fe as the catalyst for removing iron complex from gaseous hydrogen sulfide. The effects of alkalinity，EDTA/Fe molar ratio， total iron concentration， and thiosulfate concentration on the stability and desulfurization selectivity of EDTA-Fe catalyst were investigated. The experimental results showed that the degradation rate of EDTA and the selectivity of desulphurization were decreased with the increase of alkalinity value in desulphurization solution. The rise of EDTA/Fe mole ratio led to an increased EDTA degradation rate and reduced desulfurization selectivity. With the increase of total iron concentration，the degradation rate of EDTA increased， and the selectivity of desulfurization decreased. The increase of thiosulfate concentration significantly reduced the degradation rate of EDTA and increased the selectivity of desulfurization. When considering the degradation rate and selectivity of EDTA，the molar ratio of EDTA/Fe and the total iron concentration should be reduced as much as possible. In contrast，the basicity value and thiosulfate concentration in the composition of the desulfurizing solution should be appropriately increased.

Key words: composition of desulfurization solution, EDTA-Fe, stability, selectivity