Abstract: Hypersaline organic wastewater was treated with MDAT-IAT process,a novel biological process.The effect of treatment,active sludge quality,sludge settling performance and microorganism were researched.Experimental results demonstrated: under the conditions of hydraulic retention time 13.5 h,sludge retention time 20.0 d and sludge cycle rate 200%,influent NaCl mass concentration is 30～80 g/L,influent COD_Cr,BOD₅,NH₄⁺-N and PO₄^3--P are 690.3～821.8,470.0～600.0,58.4～71.9 and 2.4～4.1(mg/L) respectively.Effluent COD_Cr,BOD₅,NH₄⁺-N,PO₄^3--P and SS are 73.4～165.0,30.0～100.0,4.8～19.1,0.41～0.99 and 48.5～123.6 mg/L,respectively.When the mass concentration of NaCl is changed,the sludge amount reduces first,and then increases gradually.At the same time SVI of sludge increases gradually,and the sedimental property of sludge becomes worse gradually.