A study on the denitrification of reverse osmosis(RO) concentrated wastewater from sewage reuse treatment plant in P city was conducted using waste desulfurization agent obtained from desulfurization process. Sulfur-based autotrophic denitrifying carrier comprises the predetermined amount of waste iron sulfide (FeS, Fe2S3), mine drainage sludge and elemental sulfur showing mesoporisity with 9.9 nm (99 Å) of average pore size. Sulfur denitrifying bacteria and sulfur reducing bacteria were implanted into the pores of sulfur denitrifying carrier. Nitrate was not affected by empty bed contact time (EBCT). It is probably due to larger reducing capacity of the carrier than the concentration of nitrate in RO concentrated wastewater. Total nitrogen (T-N) removal efficiency exhibited about 90% after 4 days. Sulfate ion was surprisingly decreased with sulfur autotropic process due to the reduction of sulfate ion to HS- and S2- by sulfur reducing bacteria. Sulfide and hydrogen sulfide ions were then taken by Fe(OH)3, main component of mine drainage sludge, releasing OH-. Alkalinity was therefore maintained between 7.5 and 8.5 in pH by the released OH-. Also, it had the effect of suppressing the production of H2S, which causes bad odor.