Abstract: Na₂S, Na₂S-NaOH have been used as the absorption agent for the combined desulphurization and denitration of simulated flue gas. Both pH variation and H2 S release of the absorption solution are monitored during the combined removal process. Moreover, ions concentrations for products have been quantitative analyzed. Results obtained from the experiment are showed as follows, the Na₂S solution displayed perfect combined desulphurization and denitration performance, it acquired desulphurization efficiency closely to100% and denitration efficiency above 90%. NaNO3 can be restrained effectively by keeping the concentration of S2-to some extent, and the byproducts of Na₂SO4 and S are obtained.In addition, some Na₂S in absorption solution is oxidized by oxygen gas, the appearance of NaOH prolongs the efficient absorption time for desulphurization and denitration. This Na₂S-Na OH combined removal technology is more suitable for the flue gas with low oxygen gas.