Integrated oxidation-filtration reactor reasonably consists of a bioreactor, a slow filter and a piece of filter fabric. The activated sludge concentration in bioreactor can remain high level due to water separation from sludge by the slow filter and filter fabric. Under the sludge concentration of 9~10g/L, a good result of simultaneous nitrification and denitrification (SND) is required in the integrated oxidation-filtration reactor process with DO 1mg/L, C/N 29 and pH 7.7~8.1.